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Quadratic Equations

Class 10th Mathematics RS Aggarwal Solution
Exercise 10a
  1. x2 - x + 3 = 0 Which of the following are quadratic equations in x?…
  2. 2x^2 + 5/2 x - root 3 = 0 Which of the following are quadratic equations in x?…
  3. root 2x^2 + 7x+5 root 2 = 0 Which of the following are quadratic equations in…
  4. 1/3 x^2 + 1/5 x-2 = 0 Which of the following are quadratic equations in x?…
  5. x^2 - 3x - root x+4 = 0 Which of the following are quadratic equations in x?…
  6. x - 6/x = 3 Which of the following are quadratic equations in x?
  7. x + 2/x = x^2 Which of the following are quadratic equations in x?…
  8. x^2 - 1/x^2 = 5 Which of the following are quadratic equations in x?…
  9. (x + 2)^3 = x^3 - 8 Which of the following are quadratic equations in x?…
  10. 2x + 3)(3x + 2) = 6(x - 1)(x - 2) Which of the following are quadratic…
  11. (x + 1/x)^2 = 2 (x + 1/x) + 3 Which of the following are quadratic equations…
  12. Which of the following are the roots of 3x^2 + 2x - 1 = 0 ? (i) - 1 (ii) 1/3…
  13. Find the value of k for which x = 1 is a root of the equation x^2 + kx + 3 = 0.…
  14. Find the values of a or b for which x = 3/4 or x = - 2 are the roots of the…
  15. (2x-3) (3x + 1) = 0 Solve each of the following quadratic equations:…
  16. 4x^2 + 5x = 0 Solve each of the following quadratic equations:
  17. 3x^2 - 243 = 0 Solve each of the following quadratic equations:
  18. 2x^2 + x - 6 = 0 Solve each of the following quadratic equations:…
  19. x^2 + 6x + 5 = 0 Solve each of the following quadratic equations:…
  20. 9x^2 - 3x - 2 = 0 Solve each of the following quadratic equations:…
  21. x^2 + 12x + 35 = 0 Solve each of the following quadratic equations:…
  22. Solve each of the following quadratic equations: x^2 = 18x - 77
  23. 6x^2 + 11x + 3 = 0 Solve each of the following quadratic equations:…
  24. 6x^2 + x - 12 = 0 Solve each of the following quadratic equations:…
  25. 3x^2 - 2x - 1 = 0 Solve each of the following quadratic equations:…
  26. 4x^2 - 9x = 100 Solve each of the following quadratic equations:
  27. 15x^2 - 28 = x Solve each of the following quadratic equations:
  28. 4 - 11x = 3x^2 Solve each of the following quadratic equations:
  29. 48x^2 - 13x - 1 = 0 Solve each of the following quadratic equations:…
  30. x^2 + 2√2 x - 6 = 0 Solve each of the following quadratic equations:…
  31. √3x^2 + 10x + 7√3 = 0 Solve each of the following quadratic equations:…
  32. √3x^2 + 11x + 6√3 = 0 Solve each of the following quadratic equations:…
  33. 3√7x^2 + 4x - √7 = 0 Solve each of the following quadratic equations:…
  34. √7x^2 - 6x - 13√7 = 0 Solve each of the following quadratic equations:…
  35. 4√6x^2 - 13 x - 2√6 = 0 Solve each of the following quadratic equations:…
  36. 3x^2 - 2√6x + 2 = 0 Solve each of the following quadratic equations:…
  37. √3x^2 - 2√2x - 2√3 = 0 Solve each of the following quadratic equations:…
  38. x^2 - 3√5x + 10 = 0 Solve each of the following quadratic equations:…
  39. x^2 - (√3 + 1) x + √3 = 0 Solve each of the following quadratic equations:…
  40. x^2 + 3√3x - 30 = 0 Solve each of the following quadratic equations:…
  41. √2x^2 + 7x + 5√2 = 0 Solve each of the following quadratic equations:…
  42. 5x^2 + 13x + 8 = 0 Solve each of the following quadratic equations:…
  43. x^2 - (1+ √2)x + √2 = 0 Solve each of the following quadratic equations:…
  44. 9x^2 + 6x + 1 = 0 Solve each of the following quadratic equations:…
  45. 100x^2 - 20x + 1 = 0 Solve each of the following quadratic equations:…
  46. 2x^2 - x + 1/8 = 0 Solve each of the following quadratic equations:…
  47. 10x - 1/x = 3 Solve each of the following quadratic equations:
  48. 2/x^2 - 5/x + 2 = 0 Solve each of the following quadratic equations:…
  49. 2x^2 + ax - a^2 = 0 Solve each of the following quadratic equations:…
  50. 4x^2 + 4bx - (a^2 - b^2) = 0 Solve each of the following quadratic equations:…
  51. 4x^2 - 4a^2 x + (a^4 - b^4) = 0 Solve each of the following quadratic…
  52. x^2 + 5x - (a^2 + a - 6) = 0 Solve each of the following quadratic equations:…
  53. x^2 - 2ax - (4b^2 - a^2) = 0 Solve each of the following quadratic equations:…
  54. x^2 - (2b - 1)x + (b^2 - b - 20) = 0 Solve each of the following quadratic…
  55. x^2 + 6x - (a^2 + 2a - 8) = 0 Solve each of the following quadratic equations:…
  56. abx^2 + (b^2 - ac)x - bc = 0 Solve each of the following quadratic equations:…
  57. x^2 - 4ax - b^2 + 4a^2 = 0 Solve each of the following quadratic equations:…
  58. 4x^2 - 2 (a^2 + b^2) x + a^2 b^2 = 0 Solve each of the following quadratic…
  59. 12abx^2 - (9a^2 - 8b^2)x - 6ab = 0 Solve each of the following quadratic…
  60. a^2 b^2 x^2 + b^2 x - a^2 x - 1 = 0 Solve each of the following quadratic…
  61. 9x^2 - 9 (a + b)x + (2 a^2 + 5ab + 2b^2) = 0 Solve each of the following…
  62. 16/x - 1 = 15/x+1 , x not equal 0 ,-1 Solve each of the following quadratic…
  63. 4/x - 3 = 5/2x+3 , x not equal 0 , -3/2 Solve each of the following quadratic…
  64. 3/x+1 - 2/3x-1 = 1/2 , x not equal -1 , 1/3 Solve each of the following…
  65. 1/x-1 - 1/x+5 = 6/7 , x not equal 1 ,-5 Solve each of the following quadratic…
  66. 1/2a+b+2x = 1/2a + 1/b + 1/2x Solve each of the following quadratic equations:…
  67. x+3/x-2 - 1-x/x = 4 1/4 , x not equal 2 , 0 Solve each of the following…
  68. 3x-4/7 + 7/3x-4 = 5/2 , x not equal 4/3 Solve each of the following quadratic…
  69. x/x-1 + x-1/x = 4 1/4 , x not equal 0 , 1 Solve each of the following…
  70. x/x+1 + x+1/x = 2 4/15 , x not equal 0 , 1 Solve each of the following…
  71. x-4/x-5 + x-6/x-7 = 3 1/3 , x not equal 5 , 7 Solve each of the following…
  72. x-1/x-2 + x-3/x-4 = 3 1/3 , x not equal 2 , 4 Solve each of the following…
  73. 1/x-2 + 2/x-1 = 6/x , x not equal 0 , 1 , 2 Solve each of the following…
  74. 1/x+1 + 2/x+2 = 5/x+4 , x not equal -1 ,-2 ,-4 Solve each of the following…
  75. 3 (3x-1/2x+3) - 2 (2x+3/3x-1) = 5 , x not equal 1/3 , -3/2 Solve each of the…
  76. 3 (7x+1/5x-3) - 4 (5x-3/7x+1) = 11 , x not equal 3/5 , -1/7 Solve each of the…
  77. (4x-3/2x+1) - 10 (2x+1/4x-3) = 3 , x not equal -1/2 , 3/4 Solve each of the…
  78. (x/x+1)^2 - 5 (x/x+1) + 6 = 0 , x not equal -1 Solve each of the following…
  79. a/(x-b) + b/(x-a) = 2 , x not equal a , b Solve each of the following…
  80. a/(ax-1) + b/(bx-1) = (a+b) , x not equal 1/a , 1/b Solve each of the…
  81. 3(x + 2) + 3 - x = 10 Solve each of the following quadratic equations:…
  82. 4(x + 1) + 4(1 - x) = 10 Solve each of the following quadratic equations:…
  83. 22x - 3.2(x + 2) + 32 = 0 Solve each of the following quadratic equations:…
Exercise 10b
  1. x^2 - 6x + 3 = 0 Solve each of the following equations by using the method of…
  2. x^2 - 4x + 1 = 0 Solve each of the following equations by using the method of…
  3. x^2 + 8x - 2 = 0 Solve each of the following equations by using the method of…
  4. Solve each of the following equations by using the method of completing the…
  5. 2x^2 + 5x - 3 = 0 Solve each of the following equations by using the method of…
  6. 3x^2 - x - 2 = 0 Solve each of the following equations by using the method of…
  7. 8x^2 - 14x - 15 = 0 Solve each of the following equations by using the method…
  8. 7x^2 + 3x - 4 = 0 Solve each of the following equations by using the method of…
  9. 3x^2 - 2x - 1 = 0 Solve each of the following equations by using the method of…
  10. 5x^2 - 6x - 2 = 0 Solve each of the following equations by using the method of…
  11. 2/x^2 - 5/x + 2 = 0 Solve each of the following equations by using the method…
  12. 4x^2 + 4bx - (a^2 - b^2) = 0 Solve each of the following equations by using…
  13. x^2 - (root 2+1) x + root 2 = 0 Solve each of the following equations by using…
  14. root 2x^2 - 3x-2 root 2 = 0 Solve each of the following equations by using the…
  15. √3x^2 + 10 x + 7√3 = 0 Solve each of the following equations by using the…
  16. By using the method of completing the square, show that the equation 2x^2 + x…
Exercise 10c
  1. 2x^2 - 7x + 6 = 0 Find the discriminant of each of the following equations:…
  2. 3x^2 - 2x + 8 = 0 Find the discriminant of each of the following equations:…
  3. 2x^2 - 5√x + 4 = 0 Find the discriminant of each of the following equations:…
  4. √3x^2 + 2√2x - 2√3 = 0 Find the discriminant of each of the following…
  5. (x - 1)(2x - 1) = 0 Find the discriminant of each of the following equations:…
  6. 1 - x = 2x^2 Find the discriminant of each of the following equations:…
  7. x^2 - 4x - 1 = 0 Find the roots of each of the following equations, if they…
  8. x^2 - 6x + 4 = 0 Find the roots of each of the following equations, if they…
  9. 2x^2 + x - 4 = 0 Find the roots of each of the following equations, if they…
  10. 25x^2 + 30x + 7 = 0 Find the roots of each of the following equations, if they…
  11. 16x^2 = 24x + 1 Find the roots of each of the following equations, if they…
  12. 15x^2 - 28 = x Find the roots of each of the following equations, if they…
  13. 2x^2 - 2√2x + 1 = 0 Find the roots of each of the following equations, if they…
  14. √2x^2 + 7x + 5√2 = 0 Find the roots of each of the following equations, if they…
  15. √3x^2 + 10x - 8√3 = 0 Find the roots of each of the following equations, if…
  16. √3x^2 - 2√2x -2√3 = 0 Find the roots of each of the following equations, if…
  17. 2x^2 + 6√3x - 60 = 0 Find the roots of each of the following equations, if…
  18. 4√3x^2 + 5x - 2√3 = 0 Find the roots of each of the following equations, if…
  19. 3x^2 -2√6x + 2 = 0 Find the roots of each of the following equations, if they…
  20. 2√3x^2 - 5x + √3 = 0 Find the roots of each of the following equations, if…
  21. x^2 + x + 2 = 0 Find the roots of each of the following equations, if they…
  22. 2x^2 + ax - a^2 = 0 Find the roots of each of the following equations, if they…
  23. x^2 - (√3 + 1) x + √3 = 0 Find the roots of each of the following equations,…
  24. 2x^2 + 5√3x + 6 = 0 Find the roots of each of the following equations, if they…
  25. 3x^2 - 2x + 2 = 0 Find the roots of each of the following equations, if they…
  26. x + 1/x = 3 , x not equal 0 Find the roots of each of the following equations,…
  27. 1/x - 1/x-2 = 3 , x not equal 0 , 2 Find the roots of each of the following…
  28. x - 1/x = 3 , x not equal 0 Find the roots of each of the following equations,…
  29. m/n x^2 + n/m = 1-2x Find the roots of each of the following equations, if…
  30. 36x^2 - 12ax + (a^2 - b^2) = 0 Find the roots of each of the following…
  31. x^2 - 2ax + (a^2 - b^2) = 0 Find the roots of each of the following equations,…
  32. x^2 - 2ax - (4b^2 - a^2) = 0 Find the roots of each of the following…
  33. x^2 + 6x - (a^2 + b^2 - 8) = 0 Find the roots of each of the following…
  34. x^2 + 5x - (a^2 + a - 6) = 0 Find the roots of each of the following…
  35. x^2 - 4ax - b^2 + 4a^2 = 0 Find the roots of each of the following equations,…
  36. 4 x^2 - 4a^2 x + (a^4 - b^4) = 0 Find the roots of each of the following…
  37. 4 x^2 + 4bx - (a^2 - b^2) = 0 Find the roots of each of the following…
  38. x^2 - (2b - 1)x + (b^2 - b - 20) = 0 Find the roots of each of the following…
  39. 3a^2 x^2 + 8abx + 4b^2 = 0, a ≠ 0 Find the roots of each of the following…
  40. a^2 b^2 x^2 - (4b^4 - 3a^4)x - 12a^2 b^2 = 0, a ≠ 0 and b ≠ 0 Find the roots…
  41. 12abx^2 - (9a^2 - 8b^2)x - 6ab = 0, where a ≠ 0 and b ≠ 0 Find the roots of…
Exercise 10d
  1. 2x^2 - 8x + 5 = 0 Find the nature of the roots of the following quadratic…
  2. 3x^2 -2√6x + 2 = 0 Find the nature of the roots of the following quadratic…
  3. 5x^2 - 4x + 1 = 0 Find the nature of the roots of the following quadratic…
  4. 5x (x - 2) + 6 = 0 Find the nature of the roots of the following quadratic…
  5. 12x^2 - 4√15x + 5 = 0 Find the nature of the roots of the following quadratic…
  6. x^2 - x + 2 = 0 Find the nature of the roots of the following quadratic…
  7. If a and b are distinct real numbers, show that the quadratic equation 2 (a^2 +…
  8. Show that the roots of the equation x^2 + px - q^2 = 0 are real for all real…
  9. For what values of k are the roots of the quadratic equation 3x^2 + 2kx + 27 =…
  10. For what value of k are the roots of the quadratic equation kx(x -2√5) + 10 = 0…
  11. For what values of p are the roots of the equation 4 x^2 + px + 3 = 0 real and…
  12. Find the nonzero value of k for which the roots of the quadratic equation 9x^2…
  13. Find the values of k for which the quadratic equation (3k + 1) x^2 + 2(k + 1)x…
  14. Find the values of p for which the quadratic equation (2p + 1)x^2 - (7p + 2)x +…
  15. Find the values of p for which the quadratic equation (p + 1)x^2 - 6 (p + 1) x…
  16. If - 5 is a root of the quadratic equation 2x^2 + px - 15 = 0 and the…
  17. If 3 is a root of the quadratic equation x^2 - x + k = 0, find the value of p…
  18. If - 4 is a root of the equation x^2 + 2x + 4p = 0, find the value of k for…
  19. If the quadratic equation (1 + m^2)x^2 + 2mcx + c^2 - a^2 = 0 has equal roots,…
  20. If the roots of the equation (c^2 - ab)x^2 - 2(a^2 - bc)x + (b^2 - ac) = 0 are…
  21. Find the values of p for which the quadratic equation 2x^2 + px + 8 = 0 has…
  22. Find the value of a for which the equation (a - 12)x^2 + 2(a - 12)x + 2 = 0…
  23. Find the value of k for which the roots of 9x^2 + 8kx + 16 = 0 are real and…
  24. Find the values of k for which the given quadratic equation has real and…
  25. If a and b are real and a 1/7 b then show that the roots of the equation (a -…
  26. If the roots of the equation (a^2 + b^2)x^2 - 2 (ac + bd)x + (c^2 + d^2) = 0…
  27. If the roots of the equations ax^2 + 2bx + c = 0 and bx^2 - 2 root acx+b = 0…
Exercise 10e
  1. The sum of a natural number and its square is 156. Find the number.…
  2. The sum of a natural number and its positive square root is 132. Find the…
  3. The sum of two natural numbers is 28 and their product is 192. Find the…
  4. The sum of the squares of two consecutive positive integers is 365. Find the…
  5. The sum of the squares of two consecutive positive odd numbers is 514. Find the…
  6. The sum of the squares of two consecutive positive even numbers is 452. Find…
  7. The product of two consecutive positive integers is 306. Find the integers.…
  8. Two natural numbers differ by 3 and their product is 504. Find the numbers.…
  9. Find two consecutive multiples of 3 whose product is 648.
  10. Find two consecutive positive odd integers whose product is 483.
  11. Find two consecutive positive even integers whose product is 288.…
  12. The sum of two natural numbers is 9 and the sum of their reciprocals is 1/2.…
  13. The sum of two natural numbers is 15 and the sum of their reciprocals is 3/10.…
  14. The difference of two natural numbers is 3 and the difference of their 3…
  15. The difference of two natural numbers is 5 and the difference of their…
  16. The sum of the squares of two consecutive multiples of 7 is 1225. Find the…
  17. The sum of a natural number and its reciprocal is 65/8. Find the number.…
  18. Divide 57 into two parts whose product is 680.
  19. Divide 27 into two parts such that the sum of their reciprocals is 3/20.…
  20. Divide 16 into two parts such that twice the square of the larger part exceeds…
  21. Find two natural numbers, the sum of whose squares is 25 times their sum and…
  22. The difference of the squares of two natural numbers is 45. The square of the…
  23. Three consecutive positive integers are such that the sum of the square of the…
  24. A two - digit number is 4 times the sum of its digits and twice the product of…
  25. A two - digit number is such that the product of its digits is 14. If 45 is…
  26. The denominator of a fraction is 3 more than its numerator. The sum of the…
  27. The numerator of a fraction is 3 less than its denominator. If 1 is added to…
  28. The sum of a number and its reciprocal is 2 1/30 . Find the number.…
  29. A teacher on attempting to arrange the students for mass drill in the form of…
  30. 300 apples are distributed equally among a certain number of students. Had…
  31. In a class test, the sum of Kamal's marks in mathematics and English is 40.…
  32. Some students planned a picnic. The total budget for food was Rs. 2000. But, 5…
  33. If the price of a book is reduced by Rs. 5, a person can buy 4 more books for…
  34. A person on tour has Rs. 10800 for his expenses. If he extends his tour by 4…
  35. In a class test, the sum of the marks obtained by P in mathematics and science…
  36. A man buys a number of pens for Rs. 180. If he had bought 3 more pens for the…
  37. A dealer sells an article for Rs. 75 and gains as much per cent as the cost…
  38. One year ago, a man was 8 times as old as his son. Now, his age is equal to…
  39. The sum of the reciprocals of Meena's ages (in years) 3 years ago and 5 years…
  40. The sum of the ages of a boy and his brother is 25 years, and the product of…
  41. The product of Tanvy's age (in years) 5 years ago and her age 8 years later is…
  42. Two years ago, a man's age was three times the square of his son's age. In…
  43. A truck covers a distance of 150 km at a certain average speed and then covers…
  44. While boarding an aeroplane, a passenger got hurt. The pilot showing…
  45. A train covers a distance of 480 km at a uniform speed. If the speed had been…
  46. A train travels at a certain average speed for a distance of 54 km and then…
  47. A train travels 180 km at a uniform speed. If the speed had been 9 km/hr more,…
  48. A train covers a distance of 90 km at a uniform speed. Had the speed been 15…
  49. A passenger train takes 2 hours less for a journey of 300 km if its speed is…
  50. The distance between Mumbai and Pune is 192 km. Travelling by the Deccan…
  51. A motor boat whose speed in still water is 18 km/hr, takes 1 hour more to go…
  52. The speed of a boat in still water is 8 km/hr. It can go 15 km upstream and 22…
  53. A motorboat whose speed is 9 km/hr in still water, goes 15 km downstream and…
  54. A takes 10 days less than the time taken by B to finish a piece of work. If…
  55. Two pipes running together can fill a cistern in 3 1/13 minutes. If one pipe…
  56. Two pipes running together can fill a tank in 11 1/9 minutes. If one pipe…
  57. Two water taps together can fill a tank in 6 hours. The tap of larger diameter…
  58. The length of a rectangle is twice its breadth and its area is 288 cm^2 . Find…
  59. The length of a rectangular field is three times its breadth. If the area of…
  60. The length of a hall is 3 meters more than its breadth. If the area of the…
  61. The perimeter of a rectangular plot is 62 m and its area is 228 sq meters.…
  62. A rectangular field is 16 m long and 10 m wide. There is a path of uniform…
  63. The sum of the areas of two squares is 640 m^2 . If the difference in their…
  64. The length of a rectangle is thrice as long as the side of a square. The side…
  65. A farmer prepares a rectangular vegetable garden of area 180 sq metres. With…
  66. The area of a right triangle is 600 cm^2 . If the base of the triangle exceeds…
  67. The area of a right - angled triangle is 96 sq metres. If the base is three…
  68. The area of a right - angled triangle is 165 sq meters. Determine its base and…
  69. The hypotenuse of a right - angled triangle is 20 meters. If the difference…
  70. The length of the hypotenuse of a right - angled triangle exceeds the length…
  71. The hypotenuse of a right - angled triangle is 1 metre less than twice the…
Exercise 10f
  1. Which of the following is a quadratic equation?A. x^2 - 3√x + 2 = 0 B. x + 1/x…
  2. Which of the following is a quadratic equation?A. (x^2 + 1) = (2 - x)^2 + 3 B.…
  3. Which of the following is not a quadratic equation?A. 3x - x^2 = x^2 + 5 B. (x…
  4. If x = 3 is a solution of the equation 3x^2 + (k - 1)x + 9 = 0 then k = ?A. 11…
  5. If one root of the equation 2x^2 + ax + 6 = 0 is 2 then a = ?A. 7 B. - 7 C. 7/2…
  6. The sum of the roots of the equation x^2 - 6x + 2 = 0 isA. 2 B. - 2 C. 6 D. - 6…
  7. If the product of the roots of the equation x^2 - 3x + k = 10 is - 2 then the…
  8. The ratio of the sum and product of the roots of the equation 7x^2 - 12x + 18 =…
  9. If one root of the equation 3x^2 - 10x + 3 = 0 is 1/3 then the other root isA.…
  10. If one root of 5x^2 + 13x + k = 0 be the reciprocal of the other root then the…
  11. If the sum of the roots of the equation kx^2 + 2x + 3k = 0 is equal to their…
  12. The roots of a quadratic equation are 5 and - 2. Then, the equation isA. x^2 -…
  13. If the sum of the roots of a quadratic equation is 6 and their product is 6,…
  14. If α and β are the roots of the equation 3x^2 + 8x + 2 = 0 then (1/alpha +…
  15. The roots of the equation ax^2 + bx + c = 0 will be reciprocal of each other…
  16. If the roots of the equation ax^2 + bx + c = 0 are equal then c = ?A. - b^2/4a…
  17. If the equation 9x^2 + 6kx + 4 = 0 has equal roots then k = ?A. 2 or 0 B. - 2…
  18. If the equation x^2 + 2(k + 2)x + 9k = 0 has equal roots then k = ?A. 1 or 4…
  19. If the equation 4x^2 - 3kx + 1 = 0 has equal roots then k = ?A. plus or minus…
  20. The roots of ax^2 + bx + c = 0, a 1/7 0 are real and unequal, if (b^2 - 4ac)…
  21. In the equation ax^2 + bx + c = 0, it is given that D = (b^2 - 4ac) 0. Then,…
  22. The roots of the equation 2x^2 - 6x + 7 = 0 areA. real, unequal and rational…
  23. The roots of the equation 2x^2 - 6x + 3 = 0 areA. real, unequal and rational…
  24. If the roots of 5x^2 - kx + 1 = 0 are real and distinct thenA. -2√5 k 2√5 B. k…
  25. If the equation x^2 + 5kx + 16 = 0 has no real roots thenA. k 8/5 B. k -8/5 C.…
  26. If the equation x^2 - kx + 1 = 0 has no real roots thenA. k - 2 B. k 2 C. - 2…
  27. For what values of k, the equation kx^2 - 6x - 2 = 0 has real roots?A. k less…
  28. The sum of a number and its reciprocal is 2 1/20 . The number isA. 1/6 4/5 B.…
  29. The perimeter of a rectangle is 82 m and its area is 400 m^2 . The breadth of…
  30. The length of a rectangular field exceeds its breadth by 8 m and the area of…
  31. The roots of the quadratic equation 2x^2 - x - 6 = 0 areA. - 2, 3/2 B. 2, -3/2…
  32. The sum of two natural numbers is 8 and their product is 15. Find the numbers.…
  33. Show that x = - 3 is a solution of x^2 + 6x + 9 = 0.
  34. Show that x = - 2 is a solution of 3x^2 + 13x + 14 = 0.
  35. If x = -1/2 is a solution of the quadratic equation 3x^2 + 2kx - 3 = 0, find…
  36. Find the roots of the quadratic equation 2x^2 - x - 6 = 0.
  37. Find the solution of the quadratic equation 3√3x^2 + 10x + √3 = 0…
  38. If the roots of the quadratic equation 2x^2 + 8x + k = 0 are equal then find…
  39. If the quadratic equation px^2 -2√5px + 15 = 0 has two equal roots then find…
  40. If 1 is a root of the equation ay^2 + ay + 3 = 0 and y^2 + y + b = 0 then find…
  41. If one zero of the polynomial x^2 - 4x + 1 is (2 + √3), write the other zero.…
  42. If one root of the quadratic equation 3x^2 - 10x + k = 0 is reciprocal of the…
  43. If the roots of the quadratic equation px(x - 2) + 6 = 0 are equal, find the…
  44. Find the values of k so that the quadratic equation x^2 - 4kx + k = 0 has…
  45. Find the values of k for which the quadratic equation 9x^2 - 3kx + k = 0 has…
  46. Solve: x^2 - (root 3+1) x + root 3 = 0
  47. Solve: 2x^2 + ax - a^2 = 0
  48. Solve: 3x^2 + 5√5x - 10 = 0
  49. Solve: √3x^2 + 10x - 8√3 = 0.
  50. Solve: √3x^2 - 2√2x - 2√3 = 0
  51. Solve: 4√3x^2 + 5x -2√3 = 0
  52. Solve: 4x^2 + 4bx - (a^2 - b^2) = 0.
  53. Solve: x^2 + 5x - (a^2 + a - 6) = 0
  54. x^2 + 6x - (a^2 + 2a - 8) = 0
  55. x^2 - 4ax + 4a^2 - b^2 = 0

Exercise 10a
Question 1.

Which of the following are quadratic equations in x?

x2 - x + 3 = 0


Answer:

The given equation is a quadratic equation.


Explanation - It is of degree 2, it is in the form (a ≠ 0, a, b, c are real numbers)


where a = 1, b = - 1, c = 3.



Question 2.

Which of the following are quadratic equations in x?



Answer:

The given equation equation is a quadratic equation.

Explanation - It is of degree 2, it is in the form (a ≠ 0, a, b, c are real numbers)


where a = 2, b = , c =



Question 3.

Which of the following are quadratic equations in x?



Answer:

The given equation is a quadratic equation.

Explanation - It is of degree 2, it is in the form (a ≠ 0, a, b, c are real numbers)


where a = √2, b = 7, c = 5√2.



Question 4.

Which of the following are quadratic equations in x?



Answer:

The given equation is a quadratic equation.

Explanation - It is of degree 2, it is in the form (a ≠ 0, a, b, c are real numbers)


where a = 1/3 , b = 1/5, c = - 2.



Question 5.

Which of the following are quadratic equations in x?



Answer:

The given equation is not a quadratic equation.

Explanation - It is not in the form of because it has an extra term - √x with power 1/2



Question 6.

Which of the following are quadratic equations in x?



Answer:

The given equation is a quadratic equation.

Explanation - Given


On solving the equation it gets reduced to; ; It is of degree 2 and it is in the form (a ≠ 0, a, b, c are real numbers) where a = 1, b = - 3, c = - 6.



Question 7.

Which of the following are quadratic equations in x?



Answer:

The given equation is not a quadratic equation.

Explanation - Given


On getting reduced it becomes, it has degree = 3, it is not in the form


(a ≠ 0, a, b, c are real numbers).



Question 8.

Which of the following are quadratic equations in x?



Answer:

The given equation is not a quadratic equation.

Explanation - Given


On getting reduced it becomes ;


It is not in the form ax2 + bx + c = 0 (a ≠ 0, a, b, c are real numbers)



Question 9.

Which of the following are quadratic equations in x?

(x + 2)3 = x3 – 8


Answer:

The given equation is a quadratic equation.

Explanation Given


On getting reduced it becomes


=


Now, using


where a = 6, b = 12, c = 16


It is in the form (a ≠ 0, a, b, c are real numbers)



Question 10.

Which of the following are quadratic equations in x?

2x + 3)(3x + 2) = 6(x - 1)(x - 2)


Answer:

The given (2x + 3)(3x + 2) = 6(x - 1)(x - 2)equation is not a quadratic equation.

Explanation - Given (2x + 3)(3x + 2) = 6(x - 1)(x - 2)


On getting reduced it becomes




It is not in the form (a ≠ 0, a, b, c are real numbers)



Question 11.

Which of the following are quadratic equations in x?



Answer:

The given equation is not a quadratic equation.

Explanation - Given


On getting reduced it becomes -





It is not in the form (a ≠ 0, a, b, c are real numbers)



Question 12.

Which of the following are the roots of 3x2 + 2x - 1 = 0 ?

(i) - 1 (ii) 1/3 (iii) –1/2


Answer:

(i) - 1 is the root of given equation.

Explanation - Substituting value - 1 in LHS


=


= 3 - 2 - 1


= 3 - 3 = 0 = RHS


Value satisfies the equation or LHS = RHS.


(ii) is the root of the given euation


Explanation - Substituting value in LHS


=


=


= 1 - 1 = 0 = RHS


Value satisfies the equation or LHS = RHS.


(iii) is not the root of given equation


Explanation - Substituting value in LHS


=


=


= ≠ 0 ≠ RHS


Value does not satisfy the equation or LHS ≠ RHS.



Question 13.

Find the value of k for which x = 1 is a root of the equation x2 + kx + 3 = 0. Also, find the other root.


Answer:

Given x = 1 is a root of the equation x2 + kx + 3 = 0 it means it satisfies the equation.

Substituting x = 1 in equation -


12 + k(1) + 3 = 0




Putting the value of k in the given equation : x2 + kx + 3 = 0


This reduced to the quadratic equation x2 - 4x + 3 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation


= 1.3


= 3


And either of their sum or difference = b


= - 4


Thus the two terms are - 1 and - 3


Sum = - 1 - 3 = - 4


Product = - 1. - 3 = 3




x(x-1)-3(x-1) = 0


(x-1)(x-3) = 0


x = 1 or x = 3


Thus other root is 3.



Question 14.

Find the values of a or b for which x = 3/4 or x = - 2 are the roots of the equation

ax2 + bx – 6 = 0


Answer:

Given x = 3/4 or x = - 2 are the roots of the equation

Putting in the equation gives -



;


9a + 12b-96 = 0


3a + 4b-32 = 0 - - - - - - - - - - - - - - - (1)


putting x = - 2 in equation gives



4a-2b-6 = 0


2a-b-3 = 0


2a-3 = b - - - - - - - - - - - (2)


Substituting (2) in (1)


3a + 4(2a-3)-32 = 0


⇒ 11a-44 = 0


⇒ a = 4


⇒ b = 2(4)-3 = 5


Thus for a = 4 or b = 5; or x = - 2 are the roots of the equation



Question 15.

Solve each of the following quadratic equations:

(2x-3) (3x + 1) = 0


Answer:

(2x-3) (3x + 1) = 0


2x(3x + 1)-3(3x + 1) = 0 taking common from first two terms and last two terms


(2x-3)(3x + 1) = 0


(2x-3) = 0 or (3x + 1) = 0


x = 3/2 or x = (-1)/3


Roots of equation are 3/2, (-1)/3



Question 16.

Solve each of the following quadratic equations:

4x2 + 5x = 0


Answer:


x(4x + 5) = 0 (On taking x common)


x = 0 or (4x + 5) = 0


x = (-5)/4


Roots of equation are 0, (-5)/4



Question 17.

Solve each of the following quadratic equations:

3x2 – 243 = 0


Answer:




x = √81



Roots of equation are 9, - 9



Question 18.

Solve each of the following quadratic equations:

2x2 + x - 6 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 2; b = 1; c = -6


= 2. - 6


= - 12


And either of their sum or difference = b


= 1


Thus the two terms are 4 and - 3


Difference = 4 - 3 = 1


Product = 4. - 3 = - 12




2x(x + 2)-3(x + 2) = 0


(2x-3)(x + 2) = 0


(2x-3) = 0 or (x + 2) = 0


x = 3/2, x = -2


Roots of equation are 3/2, - 2



Question 19.

Solve each of the following quadratic equations:

x2 + 6x + 5 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1, b = 6, c = 5


= 1.5 = 5


And either of their sum or difference = b


= 6


Thus the two terms are 1 and 5


Sum = 5 + 1 = 6


Product = 5.1 = 5




x(x + 1) + 5(x + 1) = 0


(x + 1)(x + 5) = 0


(x + 1) = 0 or (x + 5) = 0


x = -1, x = -5


Roots of equation are - 1, - 5



Question 20.

Solve each of the following quadratic equations:

9x2 - 3x - 2 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 9; b = -3; c = -2


= 9. - 2 = - 18


And either of their sum or difference = b


= - 3


Thus the two terms are - 6 and 3


Sum = - 6 + 3 = - 3


Product = - 6.3 = - 18




3x(3x-2) + 1(3x-2) = 0


(3x + 1)(3x-2) = 0


(3x + 1) = 0 or (3x-2) = 0


x = (-1)/3 or x = 2/3


Roots of equation are (-1)/3, 2/3



Question 21.

Solve each of the following quadratic equations:

x2 + 12x + 35 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1; b = 12; c = 35


= 1.35 = 35


And either of their sum or difference = b


= 12


Thus the two terms are 7 and 5


Sum = 7 + 5 = 12


Product = 7.5 = 35




x(x + 7) + 5(x + 7) = 0


(x + 5)(x + 7) = 0


(x + 5) = 0 or (x + 7) = 0


x = -5 or x = -7


Roots of equation are - 5, - 7



Question 22.

Solve each of the following quadratic equations:

x2 = 18x – 77


Answer:



Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1; b = -18; c = 77


= 1.77 = 77


And either of their sum or difference = b


= - 18


Thus the two terms are - 7 and - 11


Sum = - 7 - 11 = - 18


Product = - 7. - 11 = 77




x(x-7)-11(x-7) = 0


(x-7)(x-11) = 0


(x-7) = 0 or (x-11) = 0


x = 7 or x = 11


Roots of equation are 7, 11



Question 23.

Solve each of the following quadratic equations:

6x2 + 11x + 3 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 6; b = 11; c = 3


= 6.3 = 18


And either of their sum or difference = b


= 11


Thus the two terms are 9 and 2


Sum = 9 + 2 = 11


Product = 9.2 = 18




3x(2x + 3) + 1(2x + 3) = 0


(3x + 1)(2x + 3) = 0


(3x + 1) = 0 or (2x + 3) = 0


x = (-1)/3 or x = (-3)/2


Roots of equation are ,



Question 24.

Solve each of the following quadratic equations:

6x2 + x - 12 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 6; b = 1; c = -12


= 6. - 12 = - 72


And either of their sum or difference = b


= 1


Thus the two terms are 9 and - 8


Difference = 9 - 8 = 1


Product = 9. - 8 = - 72




3x(2x + 3)-4(2x + 3) = 0


(2x + 3)(3x-4) = 0


(2x + 3) = 0 or (3x-4) = 0


x = (-3)/2 or x = 4/3


Roots of equation are ,



Question 25.

Solve each of the following quadratic equations:

3x2 - 2x - 1 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 3; b = -2; c = -1


= 3. - 1 = - 3


And either of their sum or difference = b


= - 2


Thus the two terms are - 3 and 1


Difference = - 3 + 1 = - 2


Product = - 3.1 = - 3




3x(x-1) + 1(x-1) = 0


(x-1)(3x + 1) = 0


(x-1) = 0 or (3x + 1) = 0


x = 1 or x = (-1)/3


Roots of equation are 1, (-1)/3



Question 26.

Solve each of the following quadratic equations:

4x2 - 9x = 100


Answer:



Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 4; b = -9 ; c = -100


= 4. - 100 = - 400


And either of their sum or difference = b


= - 9


Thus the two terms are - 25 and 16


Difference = - 25 + 16 = - 9


Product = - 25.16 = - 400




x(4x-25) + 4(4x-25) = 0


(4x-25)(x + 4) = 0


(4x-25) = 0 or (x + 4) = 0


x = 25/4 or x = -4


Roots of equation are 25/4, - 4



Question 27.

Solve each of the following quadratic equations:

15x2 - 28 = x


Answer:



Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 15 ; b = -1; c = -28


= 15. - 28 = - 420


And either of their sum or difference = b


= - 1


Thus the two terms are - 21 and 20


Difference = - 21 + 20 = - 1


Product = - 21.20 = - 420




3x(5x-7) + 4(5x-7) = 0


(5x-7)(3x + 4) = 0


(5x-7) = 0 or (3x + 4) = 0


x = 7/5 or x = (-4)/3


Roots of equation are 7/5, - 4/3



Question 28.

Solve each of the following quadratic equations:

4 - 11x = 3x2


Answer:



Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 3; b = 11 ;c = -4


= 3. - 4 = - 12


And either of their sum or difference = b


= 11


Thus the two terms are 12 and - 1


Difference = 12 - 1 = 11


Product = 12. - 1 = - 12




3x(x + 4)-1(x + 4) = 0


(x + 4)(3x-1) = 0


(x + 4) = 0 or (3x-1) = 0


x = -4 or x = 1/3


Roots of equation are - 4, 1/3



Question 29.

Solve each of the following quadratic equations:

48x2 - 13x - 1 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 48; b = -13 ;c = -1


= 48× - 1 = - 48


And either of their sum or difference = b


= - 13


Thus the two terms are - 16 and 3


Difference = - 16 + 3 = - 13


Product = - 16.3 = - 48




16x(3x-1) + 1(3x-1) = 0


(16x + 1)(3x-1) = 0


(16x + 1) = 0 or (3x-1) = 0


x = (-1)/6 or x = 1/3


Roots of equation are



Question 30.

Solve each of the following quadratic equations:

x2 + 2√2 x – 6 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1; b = 2√2; c = -6


= 1. - 6 = - 6


And either of their sum or difference = b


= 2√2


Thus the two terms are 3√2 and -√2


Difference = 3√2-√2 = 2√2


Product = 3√2.-√2 = 3.-2 = -6



using


x(x + 3√2)-√2(x + 3√2) = 0


(x-√2)(x + 3√2) = 0


(x-√2) = 0 or (x + 3√2) = 0


x = √2 or x = -3√2


Roots of equation are √2 or -3√2



Question 31.

Solve each of the following quadratic equations:

√3x2 + 10x + 7√3 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = √3 ;b = 10; c = 7√3


= √3.7√3 = 21


(using 3 = √3×√3)


And either of their sum or difference = b


= 10


Thus, the two terms are 7 and 3


Sum = 7 + 3 = 10


Product = 7.3 = 21



(using )






Roots of equation are



Question 32.

Solve each of the following quadratic equations:

√3x2 + 11x + 6√3 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = √(3;) b = 11; c = 6√3


= √3.6√3 = 3.6 = 18


(using 3 = √3.√3


And either of their sum or difference = b


= 11


Thus the two terms are 9 and 2


Sum = 9 + 2 = 11


Product = 9.2 = 18




√3 x(x + 3√3) + 2(x + 3√3) = 0


(using 9 = 3.3 = 3√3 √3)


(√3 x + 2)(x + 3√3) = 0


(√3 x + 2)(x + 3√3) = 0



Roots of equation are



Question 33.

Solve each of the following quadratic equations:

3√7x2 + 4x – √7 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 3√7 ;b = 4 ;c = -√7


= 3√7.-√7 = 3.-7 = -21


(using 7 = √7.√7)


And either of their sum or difference = b


= 4


Thus the two terms are 7 and - 3


Difference = 7 - 3 = 4


Product = 7× - 3 = - 21




( using 7 = √7.√7)



(√7 x-1)(3x + √7) = 0


(√7 x-1) = 0 or (3x + √7) = 0


x = 1/√7 or x = (-7)/√3


Roots of equation are



Question 34.

Solve each of the following quadratic equations:

√7x2 – 6x – 13√7 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation


= √7.-13√7 = -13.7 = -91


And either of their sum or difference = b


= - 6


Thus the two terms are 7 and - 13


Difference = - 13 + 7 = - 6


Product = 7. - 13 = - 91





x(√7 x-13) + √7 (√7 x-13) = 0


(x + √7)(√7 x-13) = 0


(x + √7) = 0 or (√7 x-13) = 0


x = -√7 or x = 13/√7


Roots of equation are



Question 35.

Solve each of the following quadratic equations:

4√6x2 – 13 x – 2√6 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 4√6 ;b = -13 ;c = -2√6


= 4√6.-2√6 = -48


And either of their sum or difference = b


= - 13


Thus the two terms are - 16 and 3


Difference = - 16 + 3 = - 13


Product = - 16.3 = - 48





(On using √6 = √3 √2 and 16 = 4.2.√2 √2 )


⇒ (4√2 x + √3)(√3 x-2√2) = 0


⇒ (4√2 x + √3) = 0 or (√3 x-2√2) = 0


x = (-√3)/(4√2 ) or x = (2√2)/√3


Roots of equation are



Question 36.

Solve each of the following quadratic equations:

3x2 – 2√6x + 2 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 3; b = -2√(6;) c = 2


= 3.2 = 6


And either of their sum or difference = b


= -2√6


Thus the two terms are -√6 and -√6


Sum = -√6 -√6 = -2√6


Product = -√6. -√6 = -6 6 = √6. √6




(On using 3 = √3.√3 and √6 = √3 √2)





Equation has repeated roots



Question 37.

Solve each of the following quadratic equations:

√3x2 – 2√2x – 2√3 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = √3 b = -2√2 c = -2√3


= √3.-2√3 = -2.3 = -6


And either of their sum or difference = b


= -2√2


Thus the two terms are -3√2 and √2


Difference = -3√2 + √2 = -2√2


Product = -3√2 × √2 = -3.2 = -6




(On using3√2 = √3 √3 √2 = √3.√6)



(∵2√3 = √2 √2 √3 = √2.√6)




Roots of equation are



Question 38.

Solve each of the following quadratic equations:

x2 – 3√5x + 10 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 ;b = -3√5 ;c = 10


= 1.10 = 10


And either of their sum or difference = b


= -3√5


Thus the two terms are -2√5 and -√5


Sum = -2√5-√5 = -3√5


Product = -2√5. -√5 = 2.5 = 10 using 5 = √5. √5




(On using: 10 = 2.5 = 2.√5 √5)


x(x-2√5)-√5 (x-2√5) = 0


(x-√5)(x-2√5) = 0


(x-√5) = 0 or (x-2√5) = 0


x = √5 or x = 2√5


Hence the roots of equation are √5 or 2√5



Question 39.

Solve each of the following quadratic equations:

x2 – (√3 + 1) x + √3 = 0


Answer:



On taking x common from first two terms and - 1 from last two


x(x-√3)-1(x-√3) = 0


(x-√3)(x-1) = 0


(x-√3) = 0 or (x-1) = 0


x = √3 or x = 1


Roots of equation are √3 or 1



Question 40.

Solve each of the following quadratic equations:

x2 + 3√3x – 30 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1; b = 3√3 ;c = -30


= 1. - 30 = - 30


And either of their sum or difference = b


= 3√3


Thus, the two terms are


Difference =


Product =








Hence the roots of equation are



Question 41.

Solve each of the following quadratic equations:

√2x2 + 7x + 5√2 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation


=


And either of their sum or difference = b


= 7


Thus the two terms are 5 and 2


Sum = 5 + 2 = 7


Product = 5.2 = 10








Hence the roots of equation are



Question 42.

Solve each of the following quadratic equations:

5x2 + 13x + 8 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 5; b = 13; c = 8


= 5.8 = 40


And either of their sum or difference = b


= 13


Thus the two terms are 5 and 8


Sum = 5 + 8 = 13


Product = 5.8 = 40







Hence the roots of equation are



Question 43.

Solve each of the following quadratic equations:

x2 – (1+ √2)x + √2 = 0


Answer:



On taking x common from first two terms and - 1 from last two






Hence the roots of equation are



Question 44.

Solve each of the following quadratic equations:

9x2 + 6x + 1 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 9; b = 6; c = 1


= 9.1 = 9


And either of their sum or difference = b


= 6


Thus the two terms are 3 and 3


Sum = 3 + 3 = 6


Product = 3.3 = 9








Hence the equation has repeated roots



Question 45.

Solve each of the following quadratic equations:

100x2 - 20x + 1 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 100 ;b = - 20 ;c = 1


= 100.1 = 100


And either of their sum or difference = b


= - 20


Thus the two terms are - 10 and - 10


Sum = - 10 - 10 = - 20


Product = - 10. - 10 = 100




10x(10x-1)-1(10x-1) = 0


(10x-1)(10x-1) = 0


(10x-1) = 0 or (10x-1) = 0



Roots of equation are repeated



Question 46.

Solve each of the following quadratic equations:



Answer:


(taking LCM)


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 16; b = - 8 ;c = 1


= 16.1 = 16


And either of their sum or difference = b


= - 8


Thus the two terms are - 4 and - 4


Sum = - 4 - 4 = - 8


Product = - 4. - 4 = 16




4x(4x-1)-1(4x-1) = 0


(4x-1)(4x-1) = 0


(4x-1) = 0 or (4x-1) = 0



The equation has repeated roots



Question 47.

Solve each of the following quadratic equations:



Answer:

taking LCM



Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 10 ;b = - 3; c = - 1


= 10. - 1 = - 10


And either of their sum or difference = b


= - 3


Thus the two terms are - 5 and 2


Difference = - 5 + 2 = - 3


Product = - 5.2 = - 10




5x(2x-1) + 1(2x-1) = 0


(5x + 1)(2x-1) = 0


(5x + 1) = 0 or (2x-1) = 0




Question 48.

Solve each of the following quadratic equations:



Answer:




Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 2; b = - 5; c = 2


= 2.2 = 4


And either of their sum or difference = b


= - 5


Thus the two terms are - 4 and - 1


Difference = - 4 - 1 = - 5


Product = - 4. - 1 = 4




2x(x-2)-1(x-2) = 0


(2x-1)(x-2) = 0


(2x-1) = 0 or (x-2) = 0



Hence the roots of equation are



Question 49.

Solve each of the following quadratic equations:

2x2 + ax - a2 = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 2; b = a; c = - a2


= - 2.a2 = - 2 a2


And either of their sum or difference = b


= a


Thus the two terms are 2a and - a


Difference = 2a - a = a


Product = 2a. - a = - 2a2




2x (x + a)-a (x + a) = 0


(2x-a) (x + a) = 0


(2x-a) = 0 or (x + a) = 0



Hence the roots of equation are



Question 50.

Solve each of the following quadratic equations:

4x2 + 4bx - (a2 - b2) = 0


Answer:


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 4 b = 4b c = - (a2 - b2)


= 4. - (a2 - b2)


= - 4a2 + 4b2


And either of their sum or difference = b


= 4b


Thus the two terms are 2(a + b) and - 2(a - b)


Difference = 2a + 2b - 2a + 2b = 4b


Product = 2(a + b). - 2(a - b) = - 4(a2 - b2)


using




⇒ 2x[2x + (a + b)]-(a-b) [2x + (a + b)] = 0


⇒ [2x + (a + b)] [2x-(a-b)] = 0


⇒ [2x + (a + b)] = 0 or [2x-(a-b)] = 0



Hence the roots of equation are



Question 51.

Solve each of the following quadratic equations:

4x2 - 4a2x + (a4 - b4) = 0


Answer:

4x2 - 4a2x + (a4 - b4) = 0

Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 4 ;b = - 4a2 ; c = (a4 - b4)


= 4. (a4 - b4)


= 4a4 - 4b4


And either of their sum or difference = b


= - 4a2


Thus the two terms are - 2(a2 + b2) and - 2(a2 - b2)


Difference = - 2(a2 + b2) - 2(a2 - b2)


= - 2a2 - 2b2 - 2a2 + 2b2


= - 4a2


Product = - 2(a2 + b2). - 2(a2 - b2)


= 4(a2 + b2)(a2 - b2)


= 4. (a4 - b4)


(∵ using a2 - b2 = (a + b) (a - b))


⇒ 4x2 - 4a2x + (a4 - b4) = 0


⇒ 4x2 - 4a2x + ((a2)2 – (b2)2) = 0


(∵ using a2 - b2 = (a + b) (a - b))


⇒ 4x2 - 2(a2 + b2) x - 2(a2 - b2) x + (a2 + b2) (a2 - b2) = 0


⇒ 2x [2x - (a2 + b2)] - (a2 - b2) [2x - (a2 + b2)] = 0


⇒ [2x - (a2 + b2)] [2x - (a2 - b2)] = 0


⇒ [2x - (a2 + b2)] = 0 or [2x - (a2 - b2)] = 0



Hence the roots of given equation are



Question 52.

Solve each of the following quadratic equations:

x2 + 5x - (a2 + a - 6) = 0


Answer:

x2 + 5x - (a2 + a - 6) = 0

Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1; b = 5; c = - (a2 + a - 6)


= 1. - (a2 + a - 6)


= - (a2 + a - 6)


And either of their sum or difference = b


= 5


Thus the two terms are (a + 3) and - (a - 2)


Difference = a + 3 –a + 2


= 5


Product = (a + 3). - (a - 2)


= - [(a + 3)(a - 2)]


= - (a2 + a - 6)


x2 + 5x - (a2 + a - 6) = 0


⇒ x 2 + (a + 3)x - (a - 2)x - (a + 3)(a - 2) = 0


⇒ x[x + (a + 3)] - (a - 2) [x + (a + 3)] = 0


⇒ [x + (a + 3)] [x - (a - 2)] = 0


⇒ [x + (a + 3)] = 0 or [x - (a - 2)] = 0


⇒ x = - (a + 3) or x = (a - 2)


Hence the roots of given equation are - (a + 3) or (a - 2)



Question 53.

Solve each of the following quadratic equations:

x2 - 2ax - (4b2 - a2) = 0


Answer:

x2 - 2ax - (4b2 - a2) = 0

Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = - 2a c = - (4b2 - a2)


= 1. - (4b2 - a2)


= - (4b2 - a2)


And either of their sum or difference = b


= - 2a


Thus the two terms are (2b - a) and - (2b + a)


Difference = 2b - a - 2b - a


= - 2a


Product = (2b - a) - (2b + a)


(∵ using a2 - b2 = (a + b) (a - b))


= - (4b2 - a2)


x2 - 2ax - (4b2 - a2) = 0


⇒ x2 + (2b - a)x - (2b + a)x - (2b - a)(2b + a) = 0


⇒ x[x + (2b - a)] - (2b + a)[x + (2b - a)] = 0


⇒ [x + (2b - a)] [x - (2b + a)] = 0


⇒ [x + (2b - a)] = 0 or [x - (2b + a)] = 0


⇒ x = (a - 2b) or x = (a + 2b)


Hence the roots of given equation are (a - 2b) or x = (a + 2b)



Question 54.

Solve each of the following quadratic equations:

x2 - (2b - 1)x + (b2 - b - 20) = 0


Answer:

x2 - (2b - 1)x + (b2 - b - 20) = 0

Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1; b = - (2b - 1); c = b2 - b - 20


= 1(b2 - b - 20)


= (b2 - b - 20)


And either of their sum or difference = b


= - (2b - 1)


Thus the two terms are - (b - 5) and - (b + 4)


Sum = - (b - 5) - (b + 4)


= - b + 5 - b - 4


= - 2b + 1


= - (2b - 1)


Product = - (b - 5) - (b + 4)


= (b - 5) (b + 4)


= b2 - b - 20


x2 - (2b - 1)x + (b2 - b - 20) = 0


⇒ x2 - (b - 5)x - (b + 4)x + (b - 5)(b + 4) = 0


⇒ x[x - (b - 5)] - (b + 4)[x - (b - 5)] = 0


⇒ [x - (b - 5)] [x - (b + 4)] = 0


⇒ [x - (b - 5)] = 0 or [x - (b + 4)] = 0


⇒ x = (b - 5) or x = (b + 4)


Hence the roots of equation are (b - 5) or (b + 4)



Question 55.

Solve each of the following quadratic equations:

x2 + 6x - (a2 + 2a - 8) = 0


Answer:

x2 + 6x - (a2 + 2a - 8) = 0

Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1; b = 6 ;c = - (a2 + 2a - 8)


= 1. - (a2 + 2a - 8)


= - (a2 + 2a - 8)


And either of their sum or difference = b


= 6


Thus the two terms are (a + 4) and - (a - 2)


Difference = a + 4 - a + 2


= 6


Product = (a + 4) - (a - 2)


= - (a2 + 2a - 8)


⇒ x2 + 6x - (a2 + 2a - 8) = 0


⇒ x2 + (a + 4)x - (a - 2)x - (a + 4)(a - 2) = 0


⇒ x [x + (a + 4)] - (a - 2) [x + (a + 4)] = 0


⇒ [x + (a + 4)] [x - (a - 2)] = 0


⇒ [x + (a + 4)] = 0 or [x - (a - 2)] = 0


x = - (a + 4) or x = (a - 2)


Hence the roots of equation are - (a + 4) or (a - 2)



Question 56.

Solve each of the following quadratic equations:

abx2 + (b2 - ac)x - bc = 0


Answer:

abx2 + (b2 - ac)x - bc = 0

abx2 + (b2 - ac)x - bc = 0


abx2 + b2x - acx - bc = 0


bx (ax + b) - c (ax + b) = 0 taking bx common from first two terms and –c from last two


(ax + b) (bx - c) = 0


(ax + b) = 0 or (bx - c) = 0



Hence the roots of equation are



Question 57.

Solve each of the following quadratic equations:

x2 - 4ax - b2 + 4a2 = 0


Answer:

x2 - 4ax - b2 + 4a2 = 0

x2 - 4ax – ((b)2 – (2a)2) = 0


{using a2 - b2 = (a + b)(a - b)}


x2 - (b + 2a)x + (b - 2a)x - (b + 2a)(b - 2a) = 0


⇒ x [x - (b + 2a)] + (b - 2a) [x - (b + 2a)] = 0


⇒ [x - (b + 2a)] [x + (b - 2a)] = 0


⇒ [x - (b + 2a)] = 0 or [x + (b - 2a)] = 0


⇒ x = (b + 2a) or x = - (b - 2a)


⇒ x = (2a + b) or x = (2a - b)


Hence the roots of equation are (2a + b) or (2a - b)



Question 58.

Solve each of the following quadratic equations:

4x2 - 2 (a2 + b2) x + a2b2 = 0


Answer:

4x2 - 2a2x - 2 b2x + a2b2 = 0

2x (2x - a2) - b2(2x - a2) = 0


(On taking 2x common from first two terms and –b2 from last two)


⇒ (2x - a2) (2x - b2) = 0


⇒ (2x - a2) = 0 or (2x - b2) = 0



Hence the roots of equation are



Question 59.

Solve each of the following quadratic equations:

12abx2 - (9a2 - 8b2)x - 6ab = 0


Answer:

12abx2 - (9a2 - 8b2)x - 6ab = 0

12abx2 - 9a2 x + 8b2x - 6ab = 0


3ax(4bx - 3a) + 2b(4bx - 3a) = 0 taking 3ax common from first two terms and 2b from last two


(4bx - 3a) (3ax + 2b) = 0


(4bx - 3a) = 0 or (3ax + 2b) = 0



Hence the roots of equation are



Question 60.

Solve each of the following quadratic equations:

a2b2x2 + b2x - a2x - 1 = 0


Answer:

a2b2x2 + b2x - a2x - 1 = 0

b2x(a2x + 1) - 1(a2x + 1) = 0 taking b2x common from first two terms and - 1 from last two


(a2x + 1) (b2x - 1) = 0


(a2x + 1) = 0 or (b2x - 1) = 0



Hence the roots of equation are



Question 61.

Solve each of the following quadratic equations:

9x2 - 9 (a + b)x + (2 a2 + 5ab + 2b2) = 0


Answer:

9x2 - 9(a + b)x + (2 a2 + 5ab + 2b2) = 0

Using the splitting middle term - the middle term of the general equation Ax2 + Bx + C is divided in two such values that:

Product = AC

For the given equation A = 9, B = - 9(a + b), C = 2a2 + 5ab + 2b2

= 9(2a2 + 5ab + 2b2)
= 9(2a2 + 4ab + ab + 2b2)
= 9[2a(a + 2b) + b(a + 2b)]
= 9(a + 2b)(2a + b)
= 3(a + 2b)3(2a + b)


Also,
3(a + 2b) + 3(2a + b) = 9(a + b)

Therefore,

9x2 - 9 (a + b) x + (2 a2 + 5ab + 2b2) = 0

9x2 - 3(2a + b)x - 3(a + 2b)x + (a + 2b) (2a + b) = 0

3x[3x - (2a + b)] - (a + 2b)[3x - (2a + b)] = 0

[3x - (2a + b)] [3x - (a + 2b)] = 0

[3x - (a + 2b)] = 0 or [3x - (2a + b)] = 0


Hence the roots of equation are


Question 62.

Solve each of the following quadratic equations:



Answer:



taking LCM



x2 + x = x + 16 cross multiplying


x2 - 16 = 0


x2 - (4)2 = 0 using a2 - b2 = (a + b)(a - b)


(x + 4) (x - 4) = 0


(x + 4) = 0 or (x - 4) = 0


x = 4 or x = - 4


Hence the roots of equation are 4, - 4.



Question 63.

Solve each of the following quadratic equations:



Answer:



taking LCM





x + 4 = 2x2 + 3x cross multiplying


2x2 + 2x - 4 = 0 taking 2 common


x2 + x - 2 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 1 c = - 2


= 1. - 2 = - 2


And either of their sum or difference = b


= 1


Thus the two terms are 2 and - 1


Difference = 2 - 1 = 1


Product = 2. - 1 = - 2


x2 + x - 2 = 0


x2 + 2x - x - 2 = 0


x(x + 2) - (x + 2) = 0


(x + 2) (x - 1) = 0


(x + 2) = 0 or (x - 1) = 0


x = - 2 or x = 1


Hence the roots of equation are - 2 or 1.



Question 64.

Solve each of the following quadratic equations:



Answer:



taking LCM



3x2 + 2x - 1 = 14x - 10 cross multiplying


3x2 - 12x + 9 = 0 taking 3 common


x2 - 4x + 3 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = - 4 c = 3


= 1.3 = 3


And either of their sum or difference = b


= - 4


Thus the two terms are - 3 and - 1


Sum = - 3 - 1 = - 4


Product = - 3. - 1 = 3


x2 - 4x + 3 = 0


x2 - 3x - x + 3 = 0


x(x - 3) - 1(x - 3) = 0


(x - 3) (x - 1) = 0


(x - 3) = 0 or (x - 1) = 0


x = 3 or x = 1


Hence the roots of equation are 3 or1.



Question 65.

Solve each of the following quadratic equations:



Answer:


taking LCM




x2 + 4x - 5 = 7 cross multiplying


x2 + 4x - 12 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 4 c = - 12


= 1. - 12 = - 12


And either of their sum or difference = b


= 4


Thus the two terms are 6 and - 2


Difference = 6 - 2 = 4


Product = 6. - 2 = - 12


x2 + 4x - 12 = 0


x2 + 6x - 2x - 12 = 0


x(x + 6) - 2(x + 6) = 0


(x + 6)(x - 2) = 0


(x + 6) = 0 or (x - 2) = 0


x = - 6 or x = 2


Hence the roots of equation are - 6 or 2.



Question 66.

Solve each of the following quadratic equations:



Answer:



taking LCM



4x2 + 4ax + 2bx = - 2ab cross multiplying


4x2 + 4ax + 2bx + 2ab = 0


4x(x + a) + 2b(x + a) = 0 taking 4x common from first two terms and 2b from last two


(x + a) (4x + 2b) = 0


(x + a) = 0 or (4x + 2b) = 0



Hence the roots of equation are



Question 67.

Solve each of the following quadratic equations:



Answer:


taking LCM





8x2 + 8 = 17x2 - 34x cross multiplying


- 9x2 + 34x + 8 = 0


9x2 - 34x - 8 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 9 b = - 34 c = - 8


= 9. - 8 = - 72


And either of their sum or difference = b


= - 34


Thus the two terms are - 36 and 2


Difference = - 36 + 2 = - 34


Product = - 36.2 = - 72


9x2 - 34x - 8 = 0


9x2 - 36x + 2x - 8 = 0


9x(x - 4) + 2 (x - 4) = 0


(9x + 2)(x - 4) = 0



Hence the roots of equation are



Question 68.

Solve each of the following quadratic equations:



Answer:

Given:

taking LCM


using (a - b)2 = a2 + b2 - 2ab


cross multiplying


18x2 - 48x + 130 = 105x - 140


18x2 - 153x + 270 = 0 taking 9 common


2x2 - 17x + 30 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 2 b = - 17 c = 30


= 2.30 = 60


And either of their sum or difference = b


= - 17


Thus the two terms are - 12 and - 5


Sum = - 12 - 5 = - 17


Product = - 12. - 5 = 60


2x2 - 17x + 30 = 0


2x2 - 12x - 5x + 30 = 0


2x(x - 6) - 5(x - 6) = 0


(x - 6) (2x - 5) = 0


(x - 6) = 0 or (2x - 5) = 0



Hence the roots of equation are



Question 69.

Solve each of the following quadratic equations:



Answer:

Given:

taking LCM


using (a - b)2 = a2 + b2 - 2ab



8x2 - 8x + 4 = 17x2 - 17x cross multiplying


9x2 - 9x - 4 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 9 b = - 9 c = - 4


= 9. - 4 = - 36


And either of their sum or difference = b


= - 9


Thus the two terms are - 12 and 3


Sum = - 12 + 3 = - 9


Product = - 12.3 = - 36


9x2 - 9x - 4 = 0


9x2 - 12x + 3x - 4 = 0


3x(3x - 4) + 1(3x - 4) = 0


(3x - 4) (3x + 1) = 0


(3x - 4) = 0 or (3x + 1) = 0



Hence the roots of equation are



Question 70.

Solve each of the following quadratic equations:



Answer:

Given: taking LCM




30x2 + 30x + 15 = 34x2 + 34x cross multiplying


4x2 + 4x - 15 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 4 b = 4 c = - 15


= 4. - 15 = - 60


And either of their sum or difference = b


= 4


Thus the two terms are 10 and - 6


Difference = 10 - 6 = 4


Product = 10. - 6 = - 60


4x2 + 4x - 15 = 0


4x2 + 10x - 6x - 15 = 0


2x(2x + 5) - 3(2x + 5) = 0


(2x + 5) (2x - 3) = 0


(2x + 5) = 0 or (2x - 3) = 0



Hence the roots of equation are



Question 71.

Solve each of the following quadratic equations:



Answer:

Given:

taking LCM





3x2 - 33x + 87 = 5x2 - 60x + 175 cross multiplying


2x2 - 27x + 88 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 2 b = - 27 c = 88


= 2.88 = 176


And either of their sum or difference = b


= - 27


Thus the two terms are - 16 and - 11


Sum = - 16 - 11 = - 27


Product = - 16. - 11 = 176


2x2 - 27x + 88 = 0


2x2 - 16x - 11x + 88 = 0


2x(x - 8) - 11(x - 8) = 0


(x - 8) (2x - 11) = 0


(x - 8) = 0 or (2x - 11) = 0



Hence the roots of equation are



Question 72.

Solve each of the following quadratic equations:



Answer:

Given:

taking LCM




cross multiplying


3x2 - 15x + 15 = 5x2 - 30x + 40


2x2 - 15x + 25 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 2 b = - 15 c = 25


= 2.25 = 50


And either of their sum or difference = b


= - 15


Thus the two terms are - 10 and - 5


Sum = - 10 - 5 = - 15


Product = - 10. - 5 = 50


2x2 - 15x + 25 = 0


2x2 - 10x - 5x + 25 = 0


2x(x - 5) - 5(x - 5) = 0


(x - 5)(2x - 5) = 0


(x - 5) = 0 or (2x - 5) = 0



Hence the roots of equation are



Question 73.

Solve each of the following quadratic equations:



Answer:

Given:

taking LCM


cross multiplying


3x2 - 5x = 6x2 - 18x + 12


3x2 - 13x + 12 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 3 b = - 13 c = 12


= 3.12 = 36


And either of their sum or difference = b


= - 13


Thus the two terms are - 9 and - 4


Sum = - 9 - 4 = - 13


Product = - 9. - 4 = 36


3x2 - 13x + 12 = 0


3 x2 - 9x - 4x + 12 = 0


3x (x - 3) - 4(x - 3) = 0


(x - 3) (3x - 4) = 0



Hence the roots of equation are



Question 74.

Solve each of the following quadratic equations:



Answer:

Given:

taking LCM



(3x + 4)(x + 4) = 5x2 + 15x + 10 cross multiplying


3x2 + 16x + 16 = 5x2 + 15x + 10


2x2 - x - 6 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 2 b = - 1 c = - 6


= 2. - 6 = - 12


And either of their sum or difference = b


= - 1


Thus the two terms are - 4 and 3


Difference = - 4 + 3 = - 1


Product = - 4.3 = 12


2x2 - x - 6 = 0


2x2 - 4x + 3x - 6 = 0


2x(x - 2) + 3(x - 2) = 0


(x - 2) (2x + 3) = 0


(x - 2) = 0 or (2x + 3) = 0



Hence the roots of equation are



Question 75.

Solve each of the following quadratic equations:



Answer:

Given:

taking LCM


using (a + b)2 = a2 + b2 + 2ab; (a - b)2 = a2 + b2 - 2ab




19x2 - 42x - 15 = 30x2 + 35x - 15 cross multiplying


11 x2 + 77x = 0


11x(x + 7) = 0 taking 11x common


11x = 0 or (x + 7) = 0


x = 0 or x = - 7


Hence the roots of equation are 0, - 7



Question 76.

Solve each of the following quadratic equations:



Answer:

Given:

taking LCM; using (a + b)2 = a2 + b2 + 2ab





47x2 + 162x - 33 = 385x2 - 176x - 33 cross multiplying


338x2 - 338x = 0


338x(x - 1) = 0 taking 338x common


338x = 0 or (x - 1) = 0


x = 1 or x = 0


Hence the roots of equation are 1, 0



Question 77.

Solve each of the following quadratic equations:



Answer:

Given:

taking LCM; using (a + b)2 = a2 + b2 + 2ab





- 24x2 - 64x - 1 = 3(8x2 - 2x - 3) cross multiplying


- 24x2 - 64x - 1 = 24x2 - 6x - 9


48 x2 + 58x - 8 = 0 taking 2 common


24 x2 + 29x - 4 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 24 b = 29 c = - 4


= 24. - 4 = - 96


And either of their sum or difference = b


= 29


Thus the two terms are 32 and - 3


Difference = 32 - 3 = 29


Product = 32. - 3 = - 96


24 x2 + 29x - 4 = 0


24 x2 + 32x - 3x - 4 = 0


8x(3x + 4) - 1(3x + 4) = 0


(3x + 4)(8x - 1) = 0


(3x + 4) = 0 or (8x - 1) = 0



Hence the roots of equation are



Question 78.

Solve each of the following quadratic equations:



Answer:

Given: - - - - - - - - (1)

Let


y2 - 5y + 6 = 0 substituting value for y in (1)


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = - 5 c = 6


= 1.6 = 6


And either of their sum or difference = b


= - 5


Thus the two terms are - 3 and - 2


Difference = - 3 - 2 = - 5


Product = - 3. - 2 = 6


y2 - 5y + 6 = 0


y2 - 3y - 2y + 6 = 0


y(y - 3) - 2 (y - 3) = 0


(y - 3)(y - 2) = 0


(y - 3) = 0 or (y - 2) = 0


y = 3 or y = 2


Case I: if y = 3



x = 3x + 3


2x + 3 = 0


x = - 3/2


Case II: if y = 2



x = 2x + 2


x = - 2



Hence the roots of equation are



Question 79.

Solve each of the following quadratic equations:



Answer:

Given:



taking - 1 with both terms



taking LCM



taking common (a - x - b)



taking LCM


(a - x + b)[2x - (a + b)] = 0


(a - x + b) = 0 or [2x - (a + b)] = 0



Hence the roots of equation are



Question 80.

Solve each of the following quadratic equations:



Answer:

Given:




taking LCM




taking common (a + b - abx)



taking LCM



(a + b - abx)[(a + b)x - 2] = 0


(a + b - abx) = 0 or [(a + b)x - 2] = 0



Hence the roots of equation are



Question 81.

Solve each of the following quadratic equations:

3(x + 2) + 3 - x = 10


Answer:

Given: 3(x + 2) + 3 - x = 10

- - - - - - - - (1)


Let 3x = y - - - - - - - - - - (2)


substituting for y in (1)


9y2 - 10y + 1 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 9 b = - 10 c = 1


= 9.1 = 9


And either of their sum or difference = b


= - 10


Thus the two terms are - 9 and - 1


Sum = - 9 - 1 = - 10


Product = - 9. - 1 = 9


9y2 - 9y - 1y + 1 = 0


9y(y - 1) - 1(y - 1) = 0


(y - 1) (9y - 1) = 0


(y - 1) = 0 or (9y - 1) = 0


y = 1 or y = 1/9


3x = 1 or 3x = 1/9


On putting value of y in equation (2)


3x = 30 or 3x = 3 - 2


x = 0 or x = - 2


Hence the roots of equation are 0, - 2



Question 82.

Solve each of the following quadratic equations:

4(x + 1) + 4(1 - x) = 10


Answer:

Given: 4(x + 1) + 4(1 - x) = 10

- - - - - - - (1)


Let 4x = y - - - - - - - - - - (2)


substituting for y in (1)


4y2 - 10y + 4 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 4 b = - 10 c = 4


= 4.4 = 16


And either of their sum or difference = b


= - 10


Thus the two terms are - 8 and - 2


Sum = - 8 - 2 = - 10


Product = - 8. - 2 = 16


4y2 - 10y + 4 = 0


4y2 - 8y - 2y + 4 = 0


4y(y - 2) - 2(y - 2) = 0


(y - 2) (4y - 2) = 0


(y - 2) = 0 or (4y - 2) = 0


y = 2 or y = 1/2


substituting the value of y in (2)


4x = 2 or 4x = 2 - 1


22x = 21 or 22x = 2 - 1


2x = 1 or 2x = - 1



Hence the roots of equation are



Question 83.

Solve each of the following quadratic equations:

22x - 3.2(x + 2) + 32 = 0


Answer:

Given: 22x - 3.2(x + 2) + 32 = 0

(2x)2 - 3.2x.22 + 32 = 0 - - - - (1)


Let 2x = y - - - - - - (2)


substituting for y in (1)


y2 - 12y + 32 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = - 12 c = 32


= 1.32 = 32


And either of their sum or difference = b


= - 12


Thus the two terms are - 8 and - 4


Sum = - 8 - 4 = - 12


Product = - 8. - 4 = 32


y2 - 8y - 4y + 32 = 0


y(y - 8) - 4(y - 8) = 0


(y - 8) (y - 4) = 0


(y - 8) = 0 or (y - 4) = 0


y = 8 or y = 4


2x = 8 or 2x = 4


substituting the value of y in (2)


2x = 23 or 2x = 22


x = 2 or x = 3


Hence the roots of equation are 2, 3




Exercise 10b
Question 1.

Solve each of the following equations by using the method of completing the square:

x2 - 6x + 3 = 0


Answer:

Given: x2 - 6x + 3 = 0

x2 - 6x = - 3


x2 - 2.x.3 + 32 = - 3 + 32 (adding 32 on both sides)


(x - 3)2 = - 3 + 9 = 6 using a2 - 2ab + b2 = (a - b)2


(taking square root on both sides)




Hence the roots of equation are



Question 2.

Solve each of the following equations by using the method of completing the square:

x2 - 4x + 1 = 0


Answer:

Given: x2 - 4x + 1 = 0

x2 - 4x = - 1


x2 - 2.x.2 + 22 = - 1 + 22 (adding 22 on both sides)


(x - 2)2 = - 1 + 4 = 3 using a2 - 2ab + b2 = (a - b)2


(taking square root on both sides)




Hence the roots of equation are



Question 3.

Solve each of the following equations by using the method of completing the square:

x2 + 8x - 2 = 0


Answer:

Given: x2 + 8x - 2 = 0

x2 + 8x = 2


x2 + 2.x.4 + 42 = 2 + 42 (adding 42 on both sides)


(x + 4)2 = 2 + 16 = 18 using a2 + 2ab + b2 = (a + b)2


(taking square root on both sides)




Hence the roots of equation are



Question 4.

Solve each of the following equations by using the method of completing the square:



Answer:

Given:


(adding on both sides)


using a2 + 2ab + b2 = (a + b)2





Hence the equation has repeated roots



Question 5.

Solve each of the following equations by using the method of completing the square:

2x2 + 5x - 3 = 0


Answer:

Given: 2x2 + 5x - 3 = 0

4x2 + 10x - 6 = 0 (multiplying both sides by 2)


4x2 + 10x = 6


(adding on both sides)


using a2 + 2ab + b2 = (a + b)2



(taking square root on both sides)






Hence the roots of equation are



Question 6.

Solve each of the following equations by using the method of completing the square:

3x2 - x - 2 = 0


Answer:

Given: 3x2 - x - 2 = 0

9x2 - 3x - 6 = 0 (multiplying both sides by 3)


9x2 - 3x = 6


(adding on both sides)


using a2 - 2ab + b2 = (a - b)2


(taking square root on both sides)





Hence the roots of equation are



Question 7.

Solve each of the following equations by using the method of completing the square:

8x2 - 14x - 15 = 0


Answer:

Given: 8x2 - 14x - 15 = 0

16x2 - 28x - 30 = 0 (multiplying both sides by 2)


16x2 - 28x = 30


(adding on both sides)


using a2 - 2ab + b2 = (a - b)2


(taking square root on both sides)





Hence the roots of equation are



Question 8.

Solve each of the following equations by using the method of completing the square:

7x2 + 3x - 4 = 0


Answer:

Given: 7x2 + 3x - 4 = 0

49x2 + 21x - 28 = 0 (multiplying both sides by 7)


(adding on both sides)


using a2 + 2ab + b2 = (a + b)2


(taking square root on both sides)





Hence the roots of equation are



Question 9.

Solve each of the following equations by using the method of completing the square:

3x2 - 2x - 1 = 0


Answer:

Given: 3x2 - 2x - 1 = 0

9x2 - 6x = 3 (multiplying both sides by 3)


(adding on both sides)


using a2 - 2ab + b2 = (a - b)2


(taking square root on both sides)


3x - 1 = 2 or 3x - 1 = - 2


3x = 3 or 3x = - 1



Hence the roots of equation are



Question 10.

Solve each of the following equations by using the method of completing the square:

5x2 - 6x - 2 = 0


Answer:

Given: 5x2 - 6x - 2 = 0

25x2 - 30x - 10 = 0 (multiplying both sides by 5)


25x2 - 30x = 10


(adding on both sides)


using a2 - 2ab + b2 = (a - b)2


(taking square root on both sides)





Hence the roots of equation are



Question 11.

Solve each of the following equations by using the method of completing the square:



Answer:

Given:


2x2 - 5x + 2 = 0


4x2 - 10x + 4 = 0


4x2 - 10x = - 4 (multiplying both sides by 2)


(adding on both sides)


using a2 - 2ab + b2 = (a - b)2


(taking square root on both sides)





Hence the roots of equation are



Question 12.

Solve each of the following equations by using the method of completing the square:

4x2 + 4bx - (a2 - b2) = 0


Answer:

4x2 + 4bx = (a2 - b2)

(adding on both sides)


using a2 + 2ab + b2 = (a + b)2


(taking square root on both sides)


2x + b = - a or 2x + b = a



Hence the roots of equation are



Question 13.

Solve each of the following equations by using the method of completing the square:



Answer:

Given :


(adding on both sides)


using a2 - 2ab + b2 = (a - b)2


taking square root on both sides




Hence the roots of equation are



Question 14.

Solve each of the following equations by using the method of completing the square:



Answer:

Given:

(multiplying both sides by )



[Adding on both sides]


using a2 - 2ab + b2 = (a - b)2


(taking square root on both sides)






Hence the roots of equation are



Question 15.

Solve each of the following equations by using the method of completing the square:

√3x2 + 10 x + 7√3 = 0


Answer:

Given:

(multiplying both sides with )



[Adding 52on both sides]


using a2 + 2ab + b2 = (a + b)2


(taking square root on both sides)






Hence the roots of equation are



Question 16.

By using the method of completing the square, show that the equation 2x2 + x + 4 = 0 has no real roots.


Answer:

2x2 + x + 4 = 0

4x2 + 2x + 8 = 0 (multiplying both sides by 2)


4x2 + 2x = - 8


[Adding on both sides]


using a2 + 2ab + b2 = (a + b)2


But cannot be negative for any real value of x


So there is no real value of x satisfying the given equation.


Hence the given equation has no real roots.




Exercise 10c
Question 1.

Find the discriminant of each of the following equations:

2x2 – 7x + 6 = 0


Answer:

Given: 2x2 – 7x + 6 = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 2, b = – 7, c = 6


Discriminant D = b2 – 4ac


= (– 7)2 – 4.2.6


= 49 – 48 = 1



Question 2.

Find the discriminant of each of the following equations:

3x2 – 2x + 8 = 0


Answer:

Given: 3x2 – 2x + 8 = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 3, b = – 2, c = 8


Discriminant D = b2 – 4ac


= (– 2)2 – 4.3.8


= 4 – 96 = – 92



Question 3.

Find the discriminant of each of the following equations:

2x2 – 5√x + 4 = 0


Answer:

Given:

Comparing with standard quadratic equation ax2 + bx + c = 0



Discriminant D = b2 – 4ac


=


= 25.2 – 32


= 50 – 32 = 18



Question 4.

Find the discriminant of each of the following equations:

√3x2 + 2√2x – 2√3 = 0


Answer:

Given:

Comparing with standard quadratic equation ax2 + bx + c = 0



Discriminant D = b2 – 4ac


=


= 8 + 24 = 32



Question 5.

Find the discriminant of each of the following equations:

(x – 1)(2x – 1) = 0


Answer:

Given: (x – 1)(2x – 1) = 0

2x2 – 3x + 1 = 0


Comparing with standard quadratic equation ax2 + bx + c = 0


a = , b = , c = – 1


Discriminant D = b2 – 4ac


= (– 3)2 – 4.2.1


= 9 – 8 = 1



Question 6.

Find the discriminant of each of the following equations:

1 – x = 2x2


Answer:

Given: 1 – x = 2x2

2x2 + x – 1 = 0


Comparing with standard quadratic equation ax2 + bx + c = 0


a = , b = 1, c = – 1


Discriminant D = b2 – 4ac


= (1)2 – 4.2. – 1


= 1 + 8 = 9



Question 7.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

x2 – 4x – 1 = 0


Answer:

Given: x2 – 4x – 1 = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 1, b = – 4, c = – 1


Discriminant D = b2 – 4ac


= (– 4)2 – 4.1. – 1


= 16 + 4 = 20 > 0


Hence the roots of equation are real.


Roots are given by





Hence the roots of equation are



Question 8.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

x2 – 6x + 4 = 0


Answer:

Given: x2 – 6x + 4 = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 1, b = – 6, c = 4


Discriminant D = b2 – 4ac


= (6)2 – 4.1.4


= 36 – 16 = 20 > 0


Hence the roots of equation are real.


Roots are given by





Hence the roots of equation are



Question 9.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

2x2 + x – 4 = 0


Answer:

Given: 2x2 + x – 4 = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 2, b = 1, c = – 4


Discriminant D = b2 – 4ac


= (1)2 – 4.2. – 4


= 1 + 32 = 33 > 0


Hence the roots of equation are real.


Roots are given by





Hence the roots of equation are



Question 10.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

25x2 + 30x + 7 = 0


Answer:

Given: 25x2 + 30x + 7 = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 25, b = 30, c = 7


Discriminant D = b2 – 4ac


= (30)2 – 4.25.7


= 900 – 700 = 200 > 0


Hence the roots of equation are real.


Roots are given by





Hence the roots of equation are



Question 11.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

16x2 = 24x + 1


Answer:

Given: 16x2 = 24x + 1

16x2 – 24x – 1 = 0


Comparing with standard quadratic equation ax2 + bx + c = 0


a = 16, b = – 24, c = – 1


Discriminant D = b2 – 4ac


= (– 24)2 – 4.16. – 1


= 576 + 64 = 640 > 0


Hence the roots of equation are real.


Roots are given by





Hence the roots of equation are



Question 12.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

15x2 – 28 = x


Answer:

Given: 15x2 – 28 = x

15x2 – x – 28 = 0


Comparing with standard quadratic equation ax2 + bx + c = 0


a = 15, b = – 1, c = – 28


Discriminant D = b2 – 4ac


= (– 1)2 – 4.15. – 28


= 1 + 1680 = 1681 > 0


Hence the roots of equation are real.


Roots are given by





Hence the roots of equation are



Question 13.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

2x2 – 2√2x + 1 = 0


Answer:

Given:

Comparing with standard quadratic equation ax2 + bx + c = 0



Discriminant D = b2 – 4ac


=


= 8 – 8 = 0


Hence the roots of equation are real.


Roots are given by





Hence these are the repeated roots of the equation



Question 14.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

√2x2 + 7x + 5√2 = 0


Answer:

Given:

Comparing with standard quadratic equation ax2 + bx + c = 0



Discriminant D = b2 – 4ac



= 49 – 40 = 9 > 0


Hence the roots of equation are real.


Roots are given by





Hence the roots of equation are



Question 15.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

√3x2 + 10x – 8√3 = 0


Answer:

Given:

Comparing with standard quadratic equation ax2 + bx + c = 0



Discriminant D = b2 – 4ac



= 100 + 96 = 196 > 0


Hence the roots of equation are real.



Roots are given by





Hence the roots of equation are



Question 16.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

√3x2 – 2√2x –2√3 = 0


Answer:

Given:

Comparing with standard quadratic equation ax2 + bx + c = 0



Discriminant D = b2 – 4ac


=


= 8 + 24 = 32 > 0


Hence the roots of equation are real.



Roots are given by





Hence the roots of equation are



Question 17.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

2x2 + 6√3x – 60 = 0


Answer:

Given:

Comparing with standard quadratic equation ax2 + bx + c = 0



Discriminant D = b2 – 4ac


=


= 180 + 480 = 588 > 0


Hence the roots of equation are real.



Roots are given by





Hence the roots of equation are



Question 18.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

4√3x2 + 5x – 2√3 = 0


Answer:

Given

Comparing with standard quadratic equation ax2 + bx + c = 0



Discriminant D = b2 – 4ac


=


= 25 + 96 = 121 > 0


Hence the roots of equation are real.



Roots are given by





Hence the roots of equation are



Question 19.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

3x2 –2√6x + 2 = 0


Answer:

Given:

Comparing with standard quadratic equation ax2 + bx + c = 0



Discriminant D = b2 – 4ac



= 24 – 24 = 0



Hence the roots of equation are real and repeated.


Roots are given by




Hence the roots of equation are



Question 20.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

2√3x2 – 5x + √3 = 0


Answer:

Given:

Comparing with standard quadratic equation ax2 + bx + c = 0



Discriminant D = b2 – 4ac


=


= 25 – 24 = 10


Hence the roots of equation are real.



Roots are given by





Hence the roots of equation are



Question 21.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

x2 + x + 2 = 0


Answer:

Given: x2 + x + 2 = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 1, b = 1, c = 2


Discriminant D = b2 – 4ac


= (1)2 – 4.1.2


= 1 – 8 = – 7 < 0


Hence the roots of equation do not exist



Question 22.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

2x2 + ax – a2 = 0


Answer:

Given: 2x2 + ax – a2 = 0

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = 2, B = a, C = – a2


Discriminant D = B2 – 4AC


= (a)2 – 4.2. – a2


= a2 + 8 a2 = 9a2 ≥0


Hence the roots of equation are real.



Roots are given by





Hence the roots of equation are



Question 23.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

x2 – (√3 + 1) x + √3 = 0


Answer:

Given:

Comparing with standard quadratic equation ax2 + bx + c = 0



Discriminant D = b2 – 4ac




Using a2 – 2ab + b2 = (a – b)2


Thus the roots of given equation are real.



Roots are given by





Hence the roots of equation are



Question 24.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

2x2 + 5√3x + 6 = 0


Answer:

Given:

Comparing with standard quadratic equation ax2 + bx + c = 0



Discriminant D = b2 – 4ac


=


= 75 – 48 = 27 >


Hence the roots of equation are real.



Roots are given by





Hence the roots of equation are



Question 25.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

3x2 – 2x + 2 = 0


Answer:

Given: 3x2 – 2x + 2 = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 3, b = – 2, c = 2


Discriminant D = b2 – 4ac


= (– 2)2 – 4.3.2


= 4 – 24 = – 20 < 0


Hence the roots of equation do not exist



Question 26.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:



Answer:

Given:

taking LCM



cross multiplying


x2 + 1 = 3x


x2 – 3x + 1 = 0


Comparing with standard quadratic equation ax2 + bx + c = 0


a = 1, b = – 3, c = 1


Discriminant D = b2 – 4ac


= (– 3)2 – 4.1.1


= 9 – 4 = 5 >


Hence the roots of equation are real.


√D = √5


Roots α and β are given by





Hence the roots of equation are



Question 27.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:



Answer:

Given:

taking LCM



3x2 – 6x + 2 = 0 cross multiplying


Comparing with standard quadratic equation ax2 + bx + c = 0


a = 3, b = – 6, c = 2


Discriminant D = b2 – 4ac


= (– 6)2 – 4.3.2


= 36 – 24 = 12 > 0


Hence the roots of equation are real.



Roots are given by





Hence the roots of equation are



Question 28.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:



Answer:

Given:

taking LCM


x2 – 3x – 1 = 0 cross multiplying


Comparing with standard quadratic equation ax2 + bx + c = 0


a = 1, b = – 3, c = – 1


Discriminant D = b2 – 4ac


= (– 3)2 – 4.1. – 1


= 9 + 4 = 13 > 0


Hence the roots of equation are real.



Roots are given by





Hence the roots of equation are



Question 29.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:



Answer:

Given:


taking LCM m2x+ n2 = mn – 2mnx


On cross multiplying


m2x+ 2mnx + n2 – mn = 0


Comparing with standard quadratic equation ax2 + bx + c = 0


a = m2, b = 2mn, c = n2 – mn


Discriminant D = b2 – 4ac


= (2mn)2 – 4.m2. (n2 – mn)


= 4m2n2 – 4m2n2 + 4m3n > 0


Hence the roots of equation are real.



Roots α and β are given by





Hence the roots of equation are



Question 30.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

36x2 – 12ax + (a2 – b2) = 0


Answer:

Given: 36x2 – 12ax + (a2 – b2) = 0

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = 36, B = – 12a, C = a2 – b2


Discriminant D = B2 – 4AC


= (– 12a)2 – 4.36.(a2 – b2)


= 144a2 – 144a2 + 144 b2 = 144 b2 > 0


Hence the roots of equation are real.



Roots are given by





Hence the roots of equation are



Question 31.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

x2 – 2ax + (a2 – b2) = 0


Answer:

Given: x2 – 2ax + (a2 – b2) = 0

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = 1, B = – 2a, C = a2 – b2


Discriminant D = B2 – 4AC


= (– 2a)2 – 4.1.(a2 – b2)


= 4a2 – 4a2 + 4 b2 = 4 b2 > 0


Hence the roots of equation are real.



Roots are given by




x = (a + b) or x = (a – b)


Hence the roots of equation are (a + b) or (a – b)



Question 32.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

x2 – 2ax – (4b2 – a2) = 0


Answer:

Given: x2 – 2ax – (4b2 – a2) = 0

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = 1, B = – 2a, C = – (4b2 – a2)


Discriminant D = B2 – 4AC


= (– 2a)2 – 4.1. – (4b2 – a2)


= 4a2 – 4a2 + 16 b2 = 16b2 > 0


Hence the roots of equation are real.



Roots are given by




x = (a + 2b) or x = (a – 2b)


Hence the roots of equation are (a + 2b) or (a – 2b)



Question 33.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

x2 + 6x – (a2 + b2 – 8) = 0


Answer:

Given: x2 + 6x – (a2 + b2 – 8) = 0

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = 1, B = 6, C = – (a2 + b2 – 8)


Discriminant D = B2 – 4AC


= (6)2 – 4.1. – (a2 + b2 – 8)


= 36+ 4a2 + 8a – 32 = 4a2 + 8a + 4


= 4(a2 + 2a + 1)


= 4(a + 1)2 > 0 Using a2 + 2ab + b2 = (a + b)2


Hence the roots of equation are real.



= 2(a + 1)


Roots are given by




x = (a – 2) or x = – (4 + a)


Hence the roots of equation are (a – 2) or – (4 + a)



Question 34.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

x2 + 5x – (a2 + a – 6) = 0


Answer:

Given: x2 + 5x – (a2 + a – 6) = 0

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = 1, B = 5, C = – (a2 + a – 6)


Discriminant D = B2 – 4AC


= (5)2 – 4.1. – (a2 + a – 6)


= 25+ 4a2 + 4a – 24 = 4a2 + 4a + 1


= (2a + 1)2 > 0 Using a2 + 2ab + b2 = (a + b)2


Hence the roots of equation are real.



= (2a + 1)


Roots are given by




x = (a – 2) or x = – (a + 3)


Hence the roots of equation are (a – 2) or x = – (a + 3)



Question 35.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

x2 – 4ax – b2 + 4a2 = 0


Answer:

Given: x2 – 4ax – b2 + 4a2 = 0

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = 1, B = – 4a, C = – b2 + 4a2


Discriminant D = B2 – 4AC


= (– 4a)2– 4.1. (– b2 + 4a2)


= 16a2 + 4b2 – 16a2 = 4 b2 > 0


Hence the roots of equation are real.



Roots are given by




x = (2a – b) or x = (2a + b)


Hence the roots of equation are (2a – b) or (2a + b)



Question 36.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

4 x2 – 4a2x + (a4 – b4) = 0


Answer:

Given: 4x2 – 4a2x + (a4 – b4) = 0

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = 4, B = – 4a2, C = (a4 – b4)


Discriminant D = B2 – 4AC


= (– 4a2)2 – 4.4. (a4 – b4)


= 16a4 + 16b4 – 16a4 = 16 b4 > 0


Hence the roots of equation are real.



Roots are given by





Hence the roots of equation are



Question 37.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

4 x2 + 4bx – (a2 – b2) = 0


Answer:

Given: 4x2 + 4bx – (a2 – b2) = 0

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = 4, B = 4b, C = – (a2 – b2)


Discriminant D = B2 – 4AC


= (4b)2 – 4.4. – (a2 – b2)


= 16b2 + 16a2 – 16b2 = 16 a2 > 0


Hence the roots of equation are real.



Roots are given by





Hence the roots of equation are



Question 38.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

x2 – (2b – 1)x + (b2 – b – 20) = 0


Answer:

Given: x2 – (2b – 1)x + (b2 – b – 20) = 0

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = 1, B = – (2b – 1), C = (b2 – b – 20)


Discriminant D = B2 – 4AC


= [ – (2b – 1)2] – 4.1. (b2 – b – 20) Using a2 – 2ab + b2 = (a – b)2


= 4b2 – 4b + 1 – 4b2 + 4b + 80 = 81 > 0


Hence the roots of equation are real.



Roots are given by




x = (b + 4) or x = (b – 5)


Hence the roots of equation are (b + 4) or (b – 5)



Question 39.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

3a2x2 + 8abx + 4b2 = 0, a ≠ 0


Answer:

Given: 3a2x2 + 8abx + 4b2 = 0

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = 3a2, B = 8ab, C = 4b2


Discriminant D = B2 – 4AC


= (8ab)2 – 4.3a2. 4b2


= 64 a2b2 – 48a2b2 = 16a2b2 > 0


Hence the roots of equation are real.



= 4ab


Roots are given by





Hence the roots of equation are



Question 40.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

a2b2x2 – (4b4 – 3a4)x – 12a2b2 = 0, a ≠ 0 and b ≠ 0


Answer:

Given: a2b2x2 – (4b4 – 3a4)x – 12a2b2 = 0

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = a2b2, B = – (4b4 – 3a4), C = – 12a2b2


Discriminant D = B2 – 4AC


= [ – (4b4 – 3a4)]2 – 4a2b2. – 12a2b2


= 16b8 – 24a4b4 + 9a8 + 48 a4b4


= 16b8 + 24a4b4 + 9a8


= (4b4 + 3a4)2 > 0 Using a2 + 2ab + b2 = (a + b)2


Hence the roots of equation are real.



=


Roots are given by





Hence the roots of equation are



Question 41.

Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

12abx2 – (9a2 – 8b2)x – 6ab = 0, where a ≠ 0 and b ≠ 0


Answer:

Given: 12abx2 – (9a2 – 8b2)x – 6ab = 0

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = 12ab, B = – (9a2 – 8b2), C = – 6ab


Discriminant D = B2 – 4AC


= [ – (9a2 – 8b2)]2 – 4.12ab. – 6ab


= 81a4 – 144a2b2 + 64b4 + 288 a2b2


= 81a4 + 144a2b2 + 64b4


= (9a2 + 8b2)2 > 0 Using a2 + 2ab + b2 = (a + b)2


Hence the roots of equation are real.



= 9a2 + 8b2


Roots are given by





Hence the roots of equation are




Exercise 10d
Question 1.

Find the nature of the roots of the following quadratic equations:

2x2 – 8x + 5 = 0


Answer:

Given: 2x2 – 8x + 5 = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 2, b = – 8, c = 5


Discriminant D = b2 – 4ac


= (– 8)2 – 4.2.5


= 64 – 40 = 24 > 0


Hence the roots of equation are real and unequal.



Question 2.

Find the nature of the roots of the following quadratic equations:

3x2 –2√6x + 2 = 0


Answer:

Given:

Comparing with standard quadratic equation ax2 + bx + c = 0



Discriminant D = b2 – 4ac



= 24 – 24 = 0


Hence the roots of equation are real and equal.



Question 3.

Find the nature of the roots of the following quadratic equations:

5x2 – 4x + 1 = 0


Answer:

Given: 5x2 – 4x + 1 = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 5, b = – 4, c = 1


Discriminant D = b2 – 4ac


= (– 4)2 – 4.5.1


= 16 – 20 = – 4 < 0


Hence the equation has no real roots.



Question 4.

Find the nature of the roots of the following quadratic equations:

5x (x – 2) + 6 = 0


Answer:

Given: 5x (x – 2) + 6 = 0

5x2 – 10x + 6 = 0


Comparing with standard quadratic equation ax2 + bx + c = 0


a = 5, b = – 10, c = 6


Discriminant D = b2 – 4ac


= (– 10)2 – 4.5.6


= 100 – 120 = – 20 < 0


Hence the equation has no real roots.



Question 5.

Find the nature of the roots of the following quadratic equations:

12x2 – 4√15x + 5 = 0


Answer:

Given:

Comparing with standard quadratic equation ax2 + bx + c = 0



Discriminant D = b2 – 4ac



= 240 – 240 = 0


Hence the equation has real and equal roots.



Question 6.

Find the nature of the roots of the following quadratic equations:

x2 – x + 2 = 0


Answer:

Given: x2 – x + 2 = 0


Comparing with standard quadratic equation ax2 + bx + c = 0


a = 1, b = – 1, c = 2


Discriminant D = b2 – 4ac


= (– 1)2 – 4.1.2


= 1 – 8 = – 7 < 0


Hence the equation has no real roots.



Question 7.

If a and b are distinct real numbers, show that the quadratic equation 2 (a2 + b2)x2 + 2(a + b)x + 1 = 0 has no real roots.


Answer:

Given: 2 (a2 + b2)x2 + 2(a + b)x + 1 = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 2 (a2 + b2), b = 2(a + b), c = 1


Discriminant D = b2 – 4ac


= [2(a + b)]2 – 4. 2 (a2 + b2).1


= 4(a2 + b2 + 2ab) – 8 a2 – 8b2


= 4a2 + 4b2 + 8ab – 8a2 – 8b2


= – 4a2 – 4b2 + 8ab


= – 4(a2 + b2 – 2ab)


= – 4(a – b)2 < 0


Hence the equation has no real roots.



Question 8.

Show that the roots of the equation x2 + px – q2 = 0 are real for all real values of p and q.


Answer:

Given equation x2 + px – q2 = 0

a = 1 b = p x = – q2


Discriminant D = b2 – 4ac


= (p)2 – 4.1. – q2


= (p2 + 4q2) > 0


Thus the roots of equation are real.



Question 9.

For what values of k are the roots of the quadratic equation 3x2 + 2kx + 27 = 0 real and equal?


Answer:

Given: 3x2 + 2kx + 27 = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 3 b = 2k c = 27


Given that the roots of equation are real and equal


Thus D = 0


Discriminant D = b2 – 4ac = 0


(2k)2 – 4.3.27 = 0


4k2 – 324 = 0


4k2 = 324


k2 = 81 taking square root on both sides


k = 9 or k = – 9


The values of k are 9, – 9 for which roots of the quadratic equation are real and equal.



Question 10.

For what value of k are the roots of the quadratic equation kx(x –2√5) + 10 = 0 real and equal?


Answer:

Given equation is


Comparing with standard quadratic equation ax2 + bx + c = 0



Given that the roots of equation are real and equal


Thus D = 0


Discriminant D = b2 – 4ac = 0



20k2 – 40k = 0


20k(k – 2) = 0


20k = 0 or (k – 2) = 0


k = 0 or k = 2


The values of k are 0, 2 for which roots of the quadratic equation are real and equal.



Question 11.

For what values of p are the roots of the equation 4 x2 + px + 3 = 0 real and equal?


Answer:

Given equation is 4 x2 + px + 3 = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 4 b = p c = 3


Given that the roots of equation are real and equal


Thus D = 0


Discriminant D = b2 – 4ac = 0


(p)2 – 4.4.3 = 0


p2 = 48




The values of p are for which roots of the quadratic equation are real and equal.



Question 12.

Find the nonzero value of k for which the roots of the quadratic equation 9x2 – 3kx + k = 0 are real and equal.


Answer:

Given equation is 9x2 – 3kx + k = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 9 b = – 3k c = k


Given that the roots of equation are real and equal


Thus D = 0


Discriminant D = b2 – 4ac = 0


(– 3k)2 – 4.9.k = 0


9 k2 – 36k = 0


9k(k – 4) = 0


9k = 0 or(k – 4) = 0


k = 0 or k = 4


But given k is non zero hence k = 4 for which roots of the quadratic equation are real and equal.



Question 13.

Find the values of k for which the quadratic equation (3k + 1) x2 + 2(k + 1)x + 1 = 0 has real and equal roots.


Answer:

Given equation is (3k + 1) x2 + 2(k + 1)x + 1 = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = (3k + 1) b = 2(k + 1) c = 1


Given that the roots of equation are real and equal


Thus D = 0


Discriminant D = b2 – 4ac = 0


(2k + 2)2 – 4.(3k + 1).1 = 0 using (a + b)2 = a2 + 2ab + b2


4k2 + 8k + 4 – 12k – 4 = 0


4k2 – 4k = 0


4k(k – 1) = 0


k = 0 (k – 1) = 0


k = 0 k = 1


The values of k are 0, 1 for which roots of the quadratic equation are real and equal.



Question 14.

Find the values of p for which the quadratic equation (2p + 1)x2 – (7p + 2)x + (7p – 3) = 0 has real and equal roots.


Answer:

Given equation is (2p + 1)x2 – (7p + 2)x + (7p – 3) = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = (2p + 1) b = – (7p + 2) c = (7p – 3)


Given that the roots of equation are real and equal


Thus D = 0


Discriminant D = b2 – 4ac = 0


[ – (7p + 2)]2 – 4.(2p + 1).(7p – 3) = 0 using (a + b)2 = a2 + 2ab + b2


(49p2 + 28p + 4) – 4(14p2 + p – 3) = 0


49p2 + 28p + 4 – 56p2 – 4p + 12 = 0


– 7p2 + 24p + 16 = 0


7p2 – 24p – 16 = 0


7p2 – 28p + 4p – 16 = 0


7p(p – 4) + 4(p – 4) = 0


(7p + 4)(p – 4) = 0


(7p + 4) = 0 or (p – 4) = 0



The values of p are for which roots of the quadratic equation are real and equal.



Question 15.

Find the values of p for which the quadratic equation (p + 1)x2 – 6 (p + 1) x + 3 (p + 9) = 0, p 1 has equal roots. Hence, find the roots of the equation.


Answer:

Given equation is (p + 1)x2 – 6 (p + 1) x + 3 (p + 9) = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = (p + 1) b = – 6(p + 1) c = 3(p + 9)


Given that the roots of equation are equal


Thus D = 0


Discriminant D = b2 – 4ac = 0


[ – 6(p + 1)]2 – 4.(p + 1).3(p + 9) = 0


36(p + 1)(p + 1) – 12(p + 1)(p + 9) = 0


12(p + 1)[3(p + 1) – (p + 9)] = 0


12(p + 1)[3p + 3 – p – 9] = 0


12(p + 1)[2p – 6] = 0


(p + 1) = 0 or [2p – 6] = 0


p = – 1 or p = 3


The values of p are – 1, 3 for which roots of the quadratic equation are real and equal.



Question 16.

If – 5 is a root of the quadratic equation 2x2 + px – 15 = 0 and the quadratic equation p (x2 + x) + k = 0 has equal roots, find the value of k.


Answer:

Given that – 5 is a root of the quadratic equation 2x2 + px – 15 = 0

2(– 5)2 – 5p – 15 = 0


5p = 35


p = 7


Given equation is p (x2 + x) + k = 0


px2 + px + k = 0


Comparing with standard quadratic equation ax2 + bx + c = 0


a = p b = p c = k


Given that the roots of equation are equal


Thus D = 0


Discriminant D = b2 – 4ac = 0


[p]2 – 4.p.k = 0


72 – 28k = 0


49 – 28k = 0



The value of k is for which roots of the quadratic equation are equal.



Question 17.

If 3 is a root of the quadratic equation x2 – x + k = 0, find the value of p so that the roots of the equation x2 + k (2x + k + 2) + p = 0 are equal.


Answer:

Given 3 is a root of the quadratic equation x2 – x + k = 0

(3)2 – 3 + k = 0


k + 6 = 0


k = – 6


Given equation is x2 + k (2x + k + 2) + p = 0


x2 + 2kx + (k2 + 2k + p) = 0


Comparing with standard quadratic equation ax2 + bx + c = 0


a = 1 b = 2k c = k2 + 2k + p


Given that the roots of equation are equal


Thus D = 0


Discriminant D = b2 – 4ac = 0


(2k)2 – 4.1. (k2 + 2k + p) = 0


4k2 – 4k2 – 8k – 4p = 0


– 8k – 4p = 0


4p = – 8k


p = – 2k


p = – 2. – 6 = 12


p = 12


The value of p is – 12 for which roots of the quadratic equation are equal.



Question 18.

If – 4 is a root of the equation x2 + 2x + 4p = 0, find the value of k for which the quadratic equation x2 + px (1 + 3k) + 7(3 + 2k) = 0 has equal roots.


Answer:

Given – 4 is a root of the equation x2 + 2x + 4p = 0

(– 4)2 + 2(– 4) + 4p = 0


8 + 4p = 0


p = – 2


The quadratic equation x2 + px (1 + 3k) + 7(3 + 2k) = 0 has equal roots


Comparing with standard quadratic equation ax2 + bx + c = 0


a = 1 b = p(1 + 3k) c = 7(3 + 2k)


Thus D = 0


Discriminant D = b2 – 4ac = 0


[p(1 + 3k)]2 – 4.1.7(3 + 2k) = 0


[ – 2(1 + 3k)]2 – 4.1.7(3 + 2k) = 0


4(1 + 6k + 9k2) – 4.7(3 + 2k) = 0 using (a + b)2 = a2 + 2ab + b2


4(1 + 6k + 9k2 – 21 – 14k) = 0


9k2 – 8k – 20 = 0


9k2 – 18k – 10k – 20 = 0


9k(k – 2) + 10(k – 2) = 0


(9k + 10)(k – 2) = 0



The value of k is for which roots of the quadratic equation are equal.



Question 19.

If the quadratic equation (1 + m2)x2 + 2mcx + c2 – a2 = 0 has equal roots, prove that c2 = a2(1 + m2) .


Answer:

The quadratic equation (1 + m2) x2 + 2mcx + c2 – a2 = 0 has equal roots

Comparing with standard quadratic equation ax2 + bx + c = 0


a = (1 + m2) b = 2mc c = c2 – a2


Thus D = 0


Discriminant D = b2 – 4ac = 0


(2mc)2 – 4.(1 + m2)(c2 – a2) = 0


4 m2c2 – 4c2 + 4a2 – 4 m2c2 + 4 m2a2 = 0


– 4c2 + 4a2 + 4m2a2 = 0


a2 + m2a2 = c2


c2 = a2 (1 + m2)


Hence proved



Question 20.

If the roots of the equation (c2 – ab)x2 – 2(a2 – bc)x + (b2 – ac) = 0 are real and equal, show that either a = 0 or (a3 + b3 + c3) = 3abc.


Answer:

Given that the roots of the equation (c2 – ab)x2 – 2(a2 – bc)x + (b2 – ac) = 0 are real and equal

Comparing with standard quadratic equation ax2 + bx + c = 0


a = (c2 – ab) b = – 2(a2 – bc) c = (b2 – ac)


Thus D = 0


Discriminant D = b2 – 4ac = 0


[ – 2(a2 – bc)]2 – 4(c2 – ab) (b2 – ac) = 0


4(a4 – 2a2bc + b2c2) – 4(b2c2 – ac3 – ab3 + a2bc) = 0


using (a – b)2 = a2 – 2ab + b2


a4 – 2a2bc + b2c2 – b2c2 + ac3 + ab3 – a2bc = 0


a4 – 3a2bc + ac3 + ab3 = 0


a (a3 – 3abc + c3 + b3) = 0


a = 0 or (a3 – 3abc + c3 + b3) = 0


Hence proved a = 0 or a3 + c3 + b3 = 3abc



Question 21.

Find the values of p for which the quadratic equation 2x2 + px + 8 = 0 has real roots.


Answer:

Given that the quadratic equation 2x2 + px + 8 = 0 has real roots

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 2 b = p c = 8


Thus D = 0


Discriminant D = b2 – 4ac≥0


(p)2 – 4.2.8≥0


(p)2 – 64≥0


p2 ≥ 64 taking square root on both sides


p≥8 or p≤ – 8


The roots of equation are real for p≥8 or p≤ – 8



Question 22.

Find the value of a for which the equation (a – 12)x2 + 2(a – 12)x + 2 = 0 has equal roots.


Answer:

Given that the quadratic equation (a – 12)x2 + 2(a – 12)x + 2 = 0 has equal roots

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = (a – 12) B = 2(a – 12) C = 2


Thus D = 0


Discriminant D = B2 – 4AC≥0


[2(a – 12)]2 – 4(a – 12)2≥0


4(a2 + 144 – 24a) – 8a + 96 = 0 using (a – b)2 = a2 – 2ab + b2


4a2 + 576 – 96a – 8a + 96 = 0


4a2 – 104a + 672 = 0


a2 – 26a + 168 = 0


a2 – 14a – 12a + 168 = 0


a(a – 14) – 12(a – 14) = 0


(a – 14)(a – 12) = 0


a = 14 or a = 12


for a = 12 the equation will become non quadratic – – (a – 12)x2 + 2(a – 12)x + 2 = 0


A, B will become zero


Thus value of a = 14 for which the equation has equal roots.



Question 23.

Find the value of k for which the roots of 9x2 + 8kx + 16 = 0 are real and equal.


Answer:

Given that the quadratic equation 9x2 + 8kx + 16 = 0 roots are real and equal.

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 9 b = 8k c = 16


Thus D = 0


Discriminant D = b2 – 4ac = 0


(8k)2 – 4.9.16 = 0


64k2 – 576 = 0


k2 = 9 taking square root both sides



Thus k = 3 or k = – 3 for which the roots are real and equal.



Question 24.

Find the values of k for which the given quadratic equation has real and distinct roots:


Answer:

(i) Given: kx2 + 6x + 1 = 0

Comparing with standard quadratic equation ax2 + bx + c = 0


a = k b = 6 c = 1


For real and distinct roots: D > 0


Discriminant D = b2 – 4ac > 0


62 – 4k > 0


36 – 4k > 0


4k < 36


k < 9


(ii) Given: x2 – kx + 9 = 0


Comparing with standard quadratic equation ax2 + bx + c = 0


a = 1 b = – k c = 9


For real and distinct roots: D > 0


Discriminant D = b2 – 4ac > 0


(– k)2 – 4.1.9 = k2 – 36 > 0


k2 > 36


k > 6or k < – 6 taking square root both sides


(iii) 9x2 + 3kx + 4 = 0


Comparing with standard quadratic equation ax2 + bx + c = 0


a = 9 b = 3k c = 4


For real and distinct roots: D > 0


Discriminant D = b2 – 4ac > 0


(3k)2 – 4.4.9 = 9k2 – 144 > 0


9k2 > 144


k2 > 16


k > 4ork < – 4 taking square root both sides


(iv) 5x2 – kx + 1 = 0


Comparing with standard quadratic equation ax2 + bx + c = 0


a = 5 b = – k c = 1


For real and distinct roots: D > 0


Discriminant D = b2 – 4ac > 0


(– k)2 – 4.5.1 = k2 – 20 > 0


k2 > 20


k > 2√5 or k < –2√5 taking square root both sides



Question 25.

If a and b are real and ab then show that the roots of the equation (a – b)x2 + 5(a + b)x – 2(a – b) = 0 are real and unequal.


Answer:

Comparing with standard quadratic equation ax2 + bx + c = 0

a = (a – b) b = 5(a + b) c = – 2(a – b)


Discriminant D = b2 – 4ac


= [5(a + b)]2 – 4(a – b)(– 2(a – b))


= 25(a + b)2 + 8(a – b)2


Since a and b are real and ab then (a + b)2 > 0 (a – b)2 > 0


8(a – b)2 > 0 – – – – (1) product of two positive numbers is always positive


25(a + b)2 > 0 – – – – (2) product of two positive numbers is always positive


Adding (1) and (2) we get


8(a – b)2 + 25(a + b)2 > 0 (sum of two positive numbers is always positive)


D > 0


Hence the roots of given equation are real and unequal.



Question 26.

If the roots of the equation (a2 + b2)x2 – 2 (ac + bd)x + (c2 + d2) = 0 are a c equal, prove that


Answer:

Given the roots of the equation are equation (a2 + b2)x2 – 2 (ac + bd)x + (c2 + d2) = 0 are equal.

Comparing with standard quadratic equation ax2 + bx + c = 0


a = (a2 + b2) b = – 2(ac + bd) c = (c2 + d2)


For real and distinct roots: D = 0


Discriminant D = b2 – 4ac = 0


[ – 2(ac + bd)]2 – 4(a2 + b2)(c2 + d2) = 0


4(a2c2 + b2d2 + 2abcd) – 4(a2c2 + a2d2 + b2c2 + b2d2) = 0


using (a + b)2 = a2 + 2ab + b2


4(a2c2 + b2d2 + 2abcd – a2c2 – a2d2 – b2c2 – b2d2) = 0


2abcd – a2d2 – b2c2 = 0


– (2abcd + a2d2 + b2c2) = 0


(ad – bc)2 = 0


ad = bc



Hence proved.



Question 27.

If the roots of the equations ax2 + 2bx + c = 0 and are simultaneously real then prove that b2 = ac.


Answer:

Given the roots of the equations ax2 + 2bx + c = 0 are real.

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = a B = 2b C = c


Discriminant D1 = B2 – 4AC ≥ 0


= (2b)2 – 4.a.c ≥ 0


= 4(b2 –ac) ≥ 0


= (b2 –ac) ≥ 0 – – – – – (1)


For the equation


Discriminant D2 = b2 – 4ac ≥ 0


=


= 4(ac – b2) ≥0


= – 4(b2–ac) ≥0


= (b2 –ac) ≥0 – – – – – (2)


The roots of the are simultaneously real if (1) and (2) are true together


b2 –ac = 0


b2 = ac


Hence proved.




Exercise 10e
Question 1.

The sum of a natural number and its square is 156. Find the number.


Answer:

Let the required number be x

According to given condition,


x + x2 = 156


x2 + x – 156 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 1 c = – 156


= 1. – 156 = – 156


And either of their sum or difference = b


= 1


Thus the two terms are 13 and – 12


Sum = 13 – 12 = 1


Product = 13. – 12 = – 156


x2 + x – 156 = 0


x2 + 13x – 12x – 156 = 0


x(x + 13) – 12 (x + 13) = 0


(x – 12) (x + 13) = 0


x = 12 or x = – 13


x cannot be negative


Hence the required natural number is 12



Question 2.

The sum of a natural number and its positive square root is 132. Find the number.


Answer:

Let the required number be x

According to given condition,



putting we get




Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 1 c = – 132


= 1. – 132 = – 132


And either of their sum or difference = b


= 1


Thus the two terms are 12 and – 11


Difference = 12 – 11 = 1


Product = 12. – 11 = – 132




y(y + 12) – 11(y + 12) = 0


(y + 12) (y – 11) = 0


(y + 12) = 0 or (y – 11) = 0


y = – 12 or y = 11 but y cannot be negative


Thus y = 11


Now


x = y squaring both sides


x = (11)2 = 121


Hence the required number is 121



Question 3.

The sum of two natural numbers is 28 and their product is 192. Find the numbers.


Answer:

Let the required number be x and 28 – x

According to given condition,


x(28 – x) = 192


x2 – 28x + 192 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 28 c = 192


= 1.192 = 192


And either of their sum or difference = b


= – 28


Thus the two terms are – 16 and – 12


Sum = – 16 – 12 = – 28


Product = – 16. – 12 = 192


x2 – 28x + 192 = 0


x2 – 16x – 12x + 192 = 0


x(x – 16) – 12(x – 16) = 0


(x – 16) (x – 12) = 0


(x – 16) = 0 or (x – 12) = 0


x = 16 or x = 12


Hence the required numbers are 16, 12



Question 4.

The sum of the squares of two consecutive positive integers is 365. Find the integers.


Answer:

Let the required two consecutive positive integers be x and x + 1

According to given condition,


x2 + (x + 1)2 = 365


x2 + x2 + 2x + 1 = 365 using (a + b)2 = a2 + 2ab + b2


2x2 + 2x – 364 = 0


x2 + x – 182 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 1 c = – 182


= 1. – 182 = – 182


And either of their sum or difference = b


= 1


Thus the two terms are 14 and – 13


Difference = 14 – 13 = 1


Product = 14. – 13 = – 182


x2 + x – 182 = 0


x2 + 14x – 13x – 182 = 0


x(x + 14) – 13(x + 14) = 0


(x + 14) (x – 13) = 0


(x + 14) = 0 or (x – 13) = 0


x = – 14 or x = 13


x = 13 (x is a positive integer)


x + 1 = 13 + 1 = 14


Thus the required two consecutive positive integers are 13, 14



Question 5.

The sum of the squares of two consecutive positive odd numbers is 514. Find the numbers.


Answer:

Let the two consecutive positive odd numbers be x and x + 2

According to given condition,


x2 + (x + 2)2 = 514


x2 + x2 + 4x + 4 = 514 using (a + b)2 = a2 + 2ab + b2


2x2 + 4x – 510 = 0


x2 + 2x – 255 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 2 c = – 255


= 1. – 255 = – 255


And either of their sum or difference = b


= 2


Thus the two terms are 17 and – 15


Difference = 17 – 15 = 2


Product = 17. – 15 = – 255


x2 + 2x – 255 = 0


x2 + 17x – 15x – 255 = 0


x(x + 17) – 15(x + 17) = 0


(x + 17) (x – 15) = 0


(x + 17) = 0 or (x – 15) = 0


x = – 17 or x = 15


x = 15 (x is positive odd number)


x + 2 = 15 + 2 = 17


Thus the two consecutive positive odd numbers are 15 and 17



Question 6.

The sum of the squares of two consecutive positive even numbers is 452. Find the numbers.


Answer:

Let the two consecutive positive even numbers be x and (x + 2)

According to given condition,


x2 + (x + 2)2 = 452


x2 + x2 + 4x + 4 = 452 using (a + b)2 = a2 + 2ab + b2


2x2 + 4x – 448 = 0


x2 + 2x – 224 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 2 c = – 224


= 1. – 224 = – 224


And either of their sum or difference = b


= 2


Thus the two terms are 16 and – 14


Difference = 16 – 14 = 2


Product = 16. – 14 = – 224


x2 + 2x – 224 = 0


x2 + 16x – 14x – 224 = 0


x(x + 16) – 14(x + 16) = 0


(x + 16) (x – 14) = 0


(x + 16) = 0 or (x – 14) = 0


x = – 16 or x = 14


x = 14 (x is positive odd number)


x + 2 = 14 + 2 = 16


Thus the two consecutive positive even numbers are 14 and 16



Question 7.

The product of two consecutive positive integers is 306. Find the integers.


Answer:

Let the two consecutive positive integers be x and (x + 1)

According to given condition,


x(x + 1) = 306


x2 + x – 306 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 1 c = – 306


= 1. – 306 = – 306


And either of their sum or difference = b


= 1


Thus the two terms are 18 and – 17


Difference = 18 – 17 = 1


Product = 18. – 17 = – 306


x2 + x – 306 = 0


x2 + 18x – 17x – 306 = 0


x(x + 18) – 17(x + 18) = 0


(x + 18) (x – 17) = 0


(x + 18) = 0 or (x – 17) = 0


x = – 18 or x = 17


but x = 17 ( x is a positive integers)


x + 1 = 17 + 1 = 18


Thus the two consecutive positive integers are 17 and 18



Question 8.

Two natural numbers differ by 3 and their product is 504. Find the numbers.


Answer:

Let the two natural numbers be x and (x + 3)

According to given condition,


x(x + 3) = 504


x2 + 3x – 504 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 3 c = – 504


= 1. – 504 = – 504


And either of their sum or difference = b


= 3


Thus the two terms are 24 and – 21


Difference = 24 – 21 = 3


Product = 24. – 21 = – 504


x2 + 3x – 504 = 0


x2 + 24x – 21x – 504 = 0


x (x + 24) – 21(x + 24) = 0


(x + 24) (x – 21) = 0


(x + 24) = 0 or (x – 21) = 0


x = – 24 or x = 21


Case I: x = 21


x + 3 = 21 + 3 = 24


The numbers are (21, 24)


Case I: x = – 24


x + 3 = – 24 + 3 = – 21


The numbers are ( – 24, – 21)



Question 9.

Find two consecutive multiples of 3 whose product is 648.


Answer:

Let the required consecutive multiples of 3 be 3x and 3(x + 1)

According to given condition,


3x.3(x + 1) = 648


9(x2 + x) = 648


x2 + x = 72


x2 + x – 72 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 1 c = – 72


= 1. – 72 = – 72


And either of their sum or difference = b


= 1


Thus the two terms are 9 and – 8


Difference = 9 – 8 = 1


Product = 9. – 8 = – 72


x2 + 9x – 8x – 72 = 0


x (x + 9) – 8(x + 9) = 0


(x + 9) (x – 8) = 0


(x + 9) = 0 or (x – 8) = 0


x = – 9 or x = 8


x = 8 (rejecting the negative values)


3x = 3.8 = 24


3(x + 1) = 3(8 + 9) = 3.9 = 27


Hence, the required numbers are 24 and 27



Question 10.

Find two consecutive positive odd integers whose product is 483.


Answer:

Let the required consecutive positive odd integers be x and (x + 2)

According to given condition,


x (x + 2) = 483


x2 + 2x – 483 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 2 c = – 483


= 1. – 483 = – 483


And either of their sum or difference = b


= 2


Thus the two terms are 23 and – 21


Difference = 23 – 21 = 2


Product = 23. – 21 = – 483


x2 + 2x – 483 = 0


x2 + 23x – 21x – 483 = 0


x (x + 23) – 21(x + 23) = 0


(x + 23) (x – 21) = 0


(x + 23) = 0 or (x – 21) = 0


x = – 23 or x = 21


x = 21 (x is a positive odd integer)


x + 2 = 21 + 2 = 23


Hence, the required integers are 21 and 23



Question 11.

Find two consecutive positive even integers whose product is 288.


Answer:

Let the two consecutive positive even integers be x and (x + 2)

According to given condition,


x (x + 2) = 288


x2 + 2x – 288 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 2 c = – 288


= 1. – 288 = – 288


And either of their sum or difference = b


= 2


Thus the two terms are 18 and – 16


Difference = 18 – 16 = 2


Product = 18. – 16 = – 288


x2 + 18x – 16x – 288 = 0


x (x + 18) – 16(x + 18) = 0


(x + 18) (x – 16) = 0


(x + 18) = 0 or (x – 16) = 0


x = – 18 or x = 16


x = 16 (x is a positive odd integer)


x + 2 = 16 + 2 = 18


Hence, the required integers are 16 and 18



Question 12.

The sum of two natural numbers is 9 and the sum of their reciprocals is 1/2. Find the numbers.


Answer:

Let the required natural numbers x and (9 – x)

According to given condition,



taking LCM



cross multiplying



Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 9 c = 18


= 1.18 = 18


And either of their sum or difference = b


= – 9


Thus the two terms are – 6 and – 3


Sum = – 6 – 3 = – 9


Product = – 6. – 3 = 18




x(x – 6) – 3(x – 6) = 0


(x – 6) (x – 3) = 0


(x – 6) = 0 or (x – 3) = 0


x = 6 or x = 3


Case I: when x = 6


9 – x = 9 – 6 = 3


Case II: when x = 3


9 – x = 9 – 3 = 6


Hence required numbers are 3 and 6.



Question 13.

The sum of two natural numbers is 15 and the sum of their reciprocals is 3/10. Find the numbers.


Answer:

Let the required natural numbers x and (15 – x)

According to given condition,



taking LCM



cross multiplying





Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 15 c = 50


= 1.50 = 50


And either of their sum or difference = b


= – 15


Thus the two terms are – 10 and – 5


Sum = – 10 – 5 = – 15


Product = – 10. – 5 = 50



x(x – 10) – 5(x – 10) = 0


(x – 5) (x – 10) = 0


(x – 5) = 0 or (x – 10) = 0


x = 5 or x = 10


Case I: when x = 5


15 – x = 15 – 5 = 10


Case II: when x = 10


15 – x = 15 – 10 = 5


Hence required numbers are 5 and 10.



Question 14.

The difference of two natural numbers is 3 and the difference of their 3 reciprocals is 3/28.Find the numbers.


Answer:

Let the required natural numbers x and (x + 3)

x < x + 3


Thus


According to given condition,



taking LCM




cross multiplying




Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 3 c = – 28


= 1. – 28 = – 28


And either of their sum or difference = b


= 3


Thus the two terms are 7 and – 4


Difference = 7 – 4 = 3


Product = 7. – 4 = – 28




x(x + 7) – 4(x + 7) = 0


(x – 4) (x + 7) = 0


(x – 4) = 0 or (x + 7) = 0


x = 4 or x = – 7


x = 4 (x < x + 3)


x + 3 = 4 + 3 = 7


Hence required numbers are 4 and 7.



Question 15.

The difference of two natural numbers is 5 and the difference of their reciprocals is 5/14. Find the numbers.


Answer:

Let the required natural numbers x and (x + 5)

x < x + 5


Thus


According to given condition,



taking LCM




cross multiplying




Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 5 c = – 14


= 1. – 14 = – 14


And either of their sum or difference = b


= 5


Thus the two terms are 7 and – 2


Difference = 7 – 2 = 5


Product = 7. – 2 = – 14



x (x + 7) – 2(x + 7) = 0


(x – 2) (x + 7) = 0


(x – 2) = 0 or (x + 7) = 0


x = 2 or x = – 7


x = 2 (x < x + 3)


x + 5 = 2 + 5 = 7


Hence required natural numbers are 2 and 7.



Question 16.

The sum of the squares of two consecutive multiples of 7 is 1225. Find the multiples.


Answer:

Let the required consecutive multiples of 7 be 7x and 7(x + 1)

According to given condition,


(7x)2 + [7(x + 1)]2 = 1225


49 x2 + 49(x2 + 2x + 1) = 1225 using (a + b)2 = a2 + 2ab + b2


49 x2 + 49x2 + 98x + 49 = 1225


98x2 + 98x–1176 = 0


x2 + x – 12 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 1 c = – 12


= 1. – 12 = – 12


And either of their sum or difference = b


= 1


Thus the two terms are 4 and – 3


Difference = 4 – 3 = 1


Product = 4. – 3 = – 12


x2 + 4x – 3x – 12 = 0


x(x + 4) – 3(x + 4) = 0


(x – 3) (x + 4) = 0


(x – 3) = 0 or (x + 4) = 0


x = 3 or x = – 4


when x = 3,


7x = 7.3 = 21


7(x + 1) = 7(3 + 1) = 7.4 = 28


Hence required multiples are 21, 28.



Question 17.

The sum of a natural number and its reciprocal is 65/8. Find the number.


Answer:

Let the required natural numbers x

According to given condition,






Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 8 b = – 65 c = 8


= 8.8 = 64


And either of their sum or difference = b


= – 65


Thus the two terms are – 64 and – 1


Difference = – 64 – 1 = – 65


Product = – 64. – 1 = 64



8x (x – 8) – 1(x – 8) = 0


(x – 8) (8x – 1) = 0


(x – 8) = 0 or (8x – 1) = 0


x = 8 or x = 1/8


x = 8 (x is a natural number)


Hence the required number is 8.



Question 18.

Divide 57 into two parts whose product is 680.


Answer:

Let the two consecutive positive even integers be x and (57 – x)

According to given condition,


x (57 – x) = 680


57x – x2 = 680


x2 – 57x – 680 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 57 c = – 680


= 1. – 680 = – 680


And either of their sum or difference = b


= – 57


Thus the two terms are – 40 and – 17


Sum = – 40 – 17 = – 57


Product = – 40. – 17 = – 680


x2 – 57x – 680 = 0


x2 – 40x – 17x – 680 = 0


x (x – 40) – 17(x – 40) = 0


(x – 40) (x – 17) = 0


(x – 40) = 0 or (x – 17) = 0


x = 40 or x = 17


When x = 40


57 – x = 57 – 40 = 17


When x = 17


57 – x = 57 – 17 = 40


Hence the required parts are 17 and 40.



Question 19.

Divide 27 into two parts such that the sum of their reciprocals is 3/20.


Answer:

Let the two parts be x and (27 – x)

According to given condition,




On taking the LCM




On Cross multiplying



Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 27 c = 180


= 1. – 180 = – 180


And either of their sum or difference = b


= – 27


Thus the two terms are – 15 and – 12


Sum = – 15 – 12 = – 27


Product = – 15. – 12 = 180



x (x – 15) – 12(x – 15) = 0


(x – 15) (x – 12) = 0


(x – 15) = 0 or (x – 12) = 0


x = 15 or x = 12


Case I: when x = 12


27 – x = 27 – 12 = 15


Case II: when x = 15


27 – x = 27 – 15 = 12


Hence required numbers are 12 and 15.



Question 20.

Divide 16 into two parts such that twice the square of the larger part exceeds the square of the smaller part by 164.


Answer:

Let the larger and the smaller parts be x and y respectively.

According to the question


x + y = 16 – – – – – (1)


2x2 = y2 + 164 – – – (2)


From (1) x = 16 – y – – – (3)


From (2) and (3) we get


2(16 – y)2 = y2 + 164


2(256 – 32y + y2) = y2 + 164 using (a + b)2 = a2 + 2ab + b2


512 – 64y + 2y2 = y2 + 164


y2 – 64y + 348 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 64 c = 348


= 1. 348 = 348


And either of their sum or difference = b


= – 64


Thus the two terms are – 58 and – 6


Sum = – 58 – 6 = – 64


Product = – 58. – 6 = 348


y2 – 64y + 348 = 0


y2 – 58y – 6y + 348 = 0


y(y – 58) – 6(y – 58) = 0


(y – 58) (y – 6) = 0


(y – 58) = 0 or (y – 6) = 0


y = 6 (y < 16)


putting the value of y in (3), we get


x = 16 – 6


= 10


Hence the two natural numbers are 6 and 10.



Question 21.

Find two natural numbers, the sum of whose squares is 25 times their sum and also equal to 50 times their difference.


Answer:

Let the two natural numbers be x and y.

According to the question


x2 + y2 = 25(x + y) – – – – – (1)


x2 + y2 = 50(x – y) – – – – (2)


From (1) and (2) we get


25(x + y) = 50(x – y)


x + y = 2(x – y)


x + y = 2x – 2y


y + 2y = 2x – x


3y = x – – – – – (3)


From (2) and (3) we get


(3y)2 + y2 = 50(3y – y)


9y2 + y2 = 50(3y – y)


10 y2 = 100y


y = 10


From (3) we have,


x = 3y = 3.10 = 30


Hence the two natural numbers are 30 and 10.



Question 22.

The difference of the squares of two natural numbers is 45. The square of the smaller number is four times the larger number. Find the numbers.


Answer:

Let the larger number be x and smaller number be y.

According to the question


x2 – y2 = 45 – – – – – (1)


y2 = 4x – – – – – – (2)


From (1) and (2) we get


x2 – 4x = 45


x2 – 4x – 45 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 4 c = – 45


= 1. – 45 = – 45


And either of their sum or difference = b


= – 4


Thus the two terms are – 9 and 5


Sum = – 9 + 5 = – 4


Product = – 9.5 = – 45


x2 – 9x + 5x – 45 = 0


x(x – 9) + 5(x – 9) = 0


(x + 5) (x – 9) = 0


(x + 5) = 0 or (x – 9) = 0


x = – 5 or x = 9


x = 9


putting the value of x in equation (2), we get


y2 = 4.9 = 36


taking square root


y = 6


Hence the two numbers are 9 and 6



Question 23.

Three consecutive positive integers are such that the sum of the square of the first and the product of the other two is 46. Find the integers.


Answer:

Let the three consecutive positive integers be x, x + 1, x + 2

According to the given condition,


x2 + (x + 1)(x + 2) = 46


x2 + x2 + 3x + 2 = 46


2x2 + 3x – 44 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 2 b = 3 c = – 44


= 2. – 44 = – 88


And either of their sum or difference = b


= 3


Thus the two terms are 11 and – 8


Sum = 11 – 8 = 3


Product = 11. – 8 = – 88


2x2 + 3x – 44 = 0


2x2 + 11x – 8x – 44 = 0


x(2x + 11) – 4(2x + 11) = 0


(2x + 11)(x – 4) = 0


x = 4 or – 11/2


x = 4 (x is a positive integers)


When x = 4


x + 1 = 4 + 1 = 5


x + 2 = 4 + 2 = 6


Hence the required integers are 4, 5, 6



Question 24.

A two – digit number is 4 times the sum of its digits and twice the product of its digits. Find the number.


Answer:

Let the digits at units and tens places be x and y respectively.

Original number = 10y + x


According to the question


10y + x = 4(x + y)


10y + x = 4x + 4y


3x – 6y = 0


x = 2y – – – – (1)


also,


10y + x = 2xy


Using (1)


10y + 2y = 2.2y.y


12y = 4y2


y = 3


From (1) we get


x = 2.3 = 6


Original number = 10y + x


= (10.3) + 6 = 36



Question 25.

A two – digit number is such that the product of its digits is 14. If 45 is added to the number, the digits interchange their places. Find the number.


Answer:

Let the digits at units and tens place be x and y respectively

xy = 14


– – – – (1)


According to the question


(10y + x) + 45 = 10x + y


9y – 9x = – 45


y – x = – 5 – – – – – (2)


From (1) and (2) we get




14 – x2 = – 5x


x2 – 5x – 14 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 5 c = – 14


= 1. – 14 = – 14


And either of their sum or difference = b


= – 5


Thus the two terms are – 7 and 2


Difference = – 7 + 2 = – 5


Product = – 7.2 = – 14


x2 – 5x – 14 = 0


x2 – 7x + 2x – 14 = 0


x(x – 7) + 2(x – 7) = 0


(x + 2)(x – 7) = 0


x = 7 or x = – 2


x = 7 (neglecting the negative part)


Putting x = 7 in equation (1) we get


y = 2


Required number = 10.2 + 7 = 27



Question 26.

The denominator of a fraction is 3 more than its numerator. The sum of the fraction and its reciprocal is . Find the fraction.


Answer:

Let the numerator be x

Denominator = x + 3


Original number =



On taking the LCM




{ using (a + b)2 = a2 + 2ab + b2}



29x2 + 87x = 20x2 + 60x + 90


9x2 + 27x – 90 = 0


9(x2 + 3x – 10) = 0


x2 + 3x – 10 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 3 c = – 10


= 1. – 10 = – 10


And either of their sum or difference = b


= 3


Thus the two terms are 5 and – 2


Difference = 5 – 2 = 3


Product = 5. – 2 = – 10


x2 + 5x – 2x – 10 = 0


x(x + 5) – 2(x + 5) = 0


(x + 5)(x – 2) = 0


(x + 5) = 0 or (x – 2) = 0


x = 2 or x = – 5


x = 2 (rejecting the negative value)


So numerator is 2


Denominator = x + 3 = 2 + 3 = 5


So required fraction is 2/5



Question 27.

The numerator of a fraction is 3 less than its denominator. If 1 is added to the denominator, the fraction is decreased by . Find the fraction.


Answer:

Let the denominator of required fraction be x

Numerator of required fraction be = x – 3


Original number =


If 1 is added to the denominator, then the new fraction will become


According to the given condition,







x2 + x = 15x – 45


x2 – 14x + 45 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 14 c = 45


= 1.45 = 45


And either of their sum or difference = b


= – 14


Thus the two terms are – 9 and – 5


Sum = – 9 – 5 = – 14


Product = – 9. – 5 = – 45


x2 – 14x + 45 = 0


x2 – 9x – 5x + 45 = 0


x(x – 9) – 5(x – 9) = 0


(x – 9)(x – 5) = 0


x = 9 or x = 5


Case I: x = 5



Case II: x = 9


(Rejected because this does not satisfy the condition given)


Hence the required fraction is



Question 28.

The sum of a number and its reciprocal is . Find the number.


Answer:

Let the required number be x.

According to the given condition,




30x2 + 30 = 61x


30x2 – 61x + 30 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 30 b = – 61 c = 30


= 30.30 = 900


And either of their sum or difference = b


= – 61


Thus the two terms are – 36 and – 25


Sum = – 36 – 25 = – 61


Product = – 36. – 25 = 900


30x2 – 36x – 25x + 30 = 0


6x(5x – 6) – 5(5x – 6) = 0


(5x – 6) (6x – 5) = 0


(5x – 6) = 0 or (6x – 5) = 0



Hence the required number is



Question 29.

A teacher on attempting to arrange the students for mass drill in the form of a solid square found that 24 students were left. When he increased the size of the square by one student, he found that he was short of 25 students. Find the number of students.


Answer:

Let there be x rows

Then the number of students in each row will also be x


Total number of students x2 + 24


According to the question,


(x + 1)2 – 25 = x2 + 24 using (a + b)2 = a2 + 2ab + b2


x2 + 2x + 1 – 25 – x2 – 24 = 0


2x – 48 = 0


x = 24


Total number of students = 242 + 24 = 576 + 24 = 600



Question 30.

300 apples are distributed equally among a certain number of students. Had there been 10 more students, each would have received one apple less. Find the number of students.


Answer:

Let the total number of students be x

According to the question



taking LCM



cross multiplying



Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 10 c = – 3000


= 1. – 3000 = – 3000


And either of their sum or difference = b


= 10


Thus the two terms are 60 and – 50


Difference = 60 – 50 = 10


Product = 60. – 50 = – 3000


x2 + 60x – 50x – 3000 = 0


x(x + 60) – 50(x + 60) = 0


(x + 60) (x – 50) = 0


(x – 50) = 0 or (x + 60) = 0


x = 50 or x = – 60


x cannot be negative thus total number of students = 50



Question 31.

In a class test, the sum of Kamal's marks in mathematics and English is 40. Had he got 3 marks more in mathematics and 4 marks less in English, the product of the marks would have been 360. Find his marks in two subjects separately.


Answer:

Let Kamal's marks in mathematics and English be x and y, respectively

According to the question


x + y = 40 – – – – – – – (1)


Also (x + 3)(y – 4) = 360


(x + 3)(40 – x – 4) = 360 from (1)


(x + 3)(36 – x) = 360


36x – x2 + 108 – 3x = 360


33x – x2 – 252 = 0


x2 – 33x + 252 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 33 c = 252


= 1. – 252 = 252


And either of their sum or difference = b


= – 33


Thus the two terms are – 21 and – 12


Sum = – 21 – 12 = – 33


Product = – 21. – 12 = 252


x2 – 33x + 252 = 0


x2 – 21x – 12x + 252 = 0


x(x – 21) – 12(x – 21) = 0


(x – 21) (x – 12) = 0


(x – 21) = 0 or (x – 12) = 0


x = 21 or x = 12


if x = 21


y = 40 – 21 = 19


Kamal's marks in mathematics and English are 21 and 19


if x = 12


y = 40 – 12 = 28


Kamal's marks in mathematics and English are 12 and 28



Question 32.

Some students planned a picnic. The total budget for food was Rs. 2000. But, 5 students failed to attend the picnic and thus the cost for food for each member increased by Rs. 20. How many students attended the picnic and how much did each student pay for the food?


Answer:

Let x be the number of students who planned picnic

Original cost of food for each member =


5 students failed to attend the picnic, so (x – 5) students attended the picnic


New cost of food for each member =


According to the question



taking LCM



x2 – 5x = 500 cross multiplying


x2 – 5x – 500 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 5 c = – 500


= 1. – 500 = – 500


And either of their sum or difference = b


= – 5


Thus the two terms are – 25 and 20


Sum = – 25 + 20 = – 5


Product = – 25.20 = – 500


x2 – 5x – 500 = 0


x2 – 25x + 20x – 500 = 0


x(x – 25) + 20(x – 25) = 0


(x + 20) (x – 25) = 0


(x + 20) = 0 or (x – 25) = 0


x = – 20 or x = 25


x cannot be negative thus x = 25


The number of students who planned picnic = x – 5 = 25 – 5 = 20


Cost of food for each member =



Question 33.

If the price of a book is reduced by Rs. 5, a person can buy 4 more books for Rs. 600. Find the original price of the book.


Answer:

Let the original price of the book be Rs x

Number of books bought at original price for 600 =


If the price of a book is reduced by Rs. 5, then new price of book is Rs (x – 5)


Number of books bought at reduced price =


According to the question – –





x2 – 5x = 750


x2 – 5x – 750 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 5 c = – 750


= 1. – 750 = – 750


And either of their sum or difference = b


= – 5


Thus the two terms are – 30 and 25


Difference = – 30 + 25 = – 5


Product = – 30.25 = – 750


x2 – 5x – 750 = 0


x2 – 30x + 25x – 750 = 0


x(x – 30) + 25(x – 30) = 0


(x + 25) (x – 30) = 0


(x + 25) = 0 or (x – 30) = 0


x = – 25 , x = 30


x = 30 (Price cannot be negative)


Hence the original price of the book is Rs 30.



Question 34.

A person on tour has Rs. 10800 for his expenses. If he extends his tour by 4 days, he has to cut down his daily expenses by Rs. 90. Find the original duration of the tour.


Answer:

Let the original duration of the tour be x days

Original daily expenses =


If he extends his tour by 4 days his daily expenses =


According to the question – –



taking LCM



x2 + 4x = 480 cross multiplying


x2 + 4x – 480 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 4 c = – 480


= 1. – 480 = – 480


And either of their sum or difference = b


= 4


Thus the two terms are 24 and – 20


Difference = 24 – 20 = 4


Product = 24. – 20 = – 480


x2 + 24x – 20x – 480 = 0


x(x + 24) – 20(x + 24) = 0


(x + 24) (x – 20) = 0


(x + 24) = 0 or (x – 20) = 0


x = – 24, x = 20


x = 20 (number of days cannot be negative)


Hence the original price of tour is 20 days



Question 35.

In a class test, the sum of the marks obtained by P in mathematics and science is 28. Had he got 3 more marks in mathematics and 4 marks less in science, the product of marks obtained in the two subjects would have been 180. Find the marks obtained by him in the two subjects separately.


Answer:

Let the marks obtained by P in mathematics and science be x and (28 – x) respectively

According to the given condition,


(x + 3)(28 – x – 4) = 180


(x + 3)(24 – x) = 180


– x2 + 21x + 72 = 180


x2 – 21x + 108 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 21 c = 108


= 1.108 = 108


And either of their sum or difference = b


= – 21


Thus the two terms are – 12 and – 9


Difference = – 12 – 9 = – 21


Product = – 12. – 9 = 108


x2 – 12x – 9x + 108 = 0


x (x – 12) – 9 (x – 12) = 0


(x – 12) (x – 9) = 0


(x – 12) = 0 or (x – 9) = 0


x = 12, x = 9


When x = 12,


28 – x = 28 – 12 = 16


When x = 9,


28 – x = 28 – 9 = 19


Hence he obtained 12 marks in mathematics and 16 science or


He obtained 9 marks in mathematics and 19 science.



Question 36.

A man buys a number of pens for Rs. 180. If he had bought 3 more pens for the same amount, each pen would have cost him Rs. 3 less. How many pens did he buy?


Answer:

Let the total number of pens be x

According to the question – –



taking LCM



540 = 3x2 + 9x cross multiplying


3x2 + 9x – 540 = 0


x2 + 3x – 180 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 3 c = – 180


= 1. – 108 = – 180


And either of their sum or difference = b


= 3


Thus the two terms are 15 and – 12


Difference = 15 – 12 = 3


Product = 15. – 12 = – 180


x2 + 15x – 12x – 180 = 0


x(x + 15) – 12(x + 15) = 0


(x + 15)(x – 12) = 0


(x + 15) = 0 or (x – 12) = 0


x = – 15, x = 12


x = 12 (Total number of pens cannot be negative)


Hence the Total number of pens is 12



Question 37.

A dealer sells an article for Rs. 75 and gains as much per cent as the cost price of the article. Find the cost price of the article.


Answer:

Let the cost price of the article be x

Gain percent x%

According to the given condition,


(cost price + gain = selling price)


taking LCM

by cross multiplying

x2 + 100x = 7500


x2 + 100x – 7500 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 100 c = – 7500


= 1. – 7500 = – 7500


And either of their sum or difference = b


= 100


Thus the two terms are 150 and – 50


Difference = 150 – 50 = 100


Product = 150. – 50 = – 7500


x2 + 150x – 50x – 7500 = 0


x(x + 150) – 50(x + 150) = 0


(x + 150) (x – 50) = 0


(x + 150) = 0 or (x – 50) = 0


x = 50 (x ≠ - 150 as price cannot be negative)


Hence the cost price of the article is Rs 50


Question 38.

One year ago, a man was 8 times as old as his son. Now, his age is equal to the square of his son's age. Find their present ages.


Answer:

Let the present age of son be x years

The present age of man = x2 years


One year ago age of son = (x – 1)years


age of man = (x2 – 1)years


According to given question, One year ago, a man was 8 times as old as his son

x2 – 1 = 8(x – 1)

x2 – 1 = 8x – 8

x2 – 8x + 7 = 0

x2 – 7x – x + 7 = 0

x(x – 7) – 1(x – 7) = 0

(x – 7) (x – 1) = 0

x = 1 or x = 7

Man’s age cannot be 1 year

Thus x = 7

Thus the present age of son is 7 years

The present age of man is 72 = 49 years


Question 39.

The sum of the reciprocals of Meena's ages (in years) 3 years ago and 5 years hence is 1/3. Find her present age.


Answer:

Let the present age of Meena be x years

Meena’s age three years ago = (x – 3) years


Meena’s age five years hence = (x + 5) years


According to given question





x2 + 2x – 15 = 6x + 6


x2 – 4x – 21 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 4 c = – 21


= 1. – 21 = – 21


And either of their sum or difference = b


= – 4


Thus the two terms are – 7 and 3


Sum = – 7 + 3 = – 4


Product = – 7.3 = – 21


x2 – 7x + 3x – 21 = 0


x (x – 7) + 3(x – 7) = 0


(x – 7) (x + 3) = 0


x = – 3 or x = 7


x = 7 age cannot be negative


Hence the present age of Meena is 7 years



Question 40.

The sum of the ages of a boy and his brother is 25 years, and the product of their ages in years is 126. Find their ages.


Answer:

Let the present age of boy and his brother be x years and (25 – x) years

According to given question


x(25 – x) = 126


25x – x2 = 126


x2 – 25x + 126 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 25 c = 126


= 1.126 = 126


And either of their sum or difference = b


= – 25


Thus the two terms are – 18 and – 7


Sum = – 18 – 7 = – 25


Product = – 18. – 7 = 126


x2 – 18x – 7x + 126 = 0


x (x – 18) – 7(x – 18) = 0


(x – 18) (x – 7) = 0


x = 18 or x = 7


x = 18 (Present age of boy cannot be less than his brother)


if x = 18


The present age of boy is 18 years and his brother is (25 – 18) = 7years



Question 41.

The product of Tanvy's age (in years) 5 years ago and her age 8 years later is 30. Find her present age.


Answer:

Let the present age of Tanvy be x years

Tanvy’s age five years ago = (x – 5) years


Tanvy’s age eight years from now = (x + 8) years


(x – 5)(x + 8) = 30


x2 + 3x – 40 = 30


x2 + 3x – 70 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 3 c = – 70


= 1. – 70 = – 70


And either of their sum or difference = b


= 3


Thus the two terms are 10 and – 7


Difference = 10 – 7 = 3


Product = 10. – 7 = – 70


x2 + 10x – 7x – 70 = 0


x (x + 10) – 7(x + 10) = 0


(x + 10) (x – 7) = 0


x = – 10 or x = 7 (age cannot be negative)


x = 7


The present age of Tanvy is 7 years



Question 42.

Two years ago, a man's age was three times the square of his son's age. In three years’ time, his age will be four times his son's age. Find their present ages.


Answer:

Let son’s age 2 years ago be x years, Then

man’s age 2 years ago be 3x2 years


son’s present age = (x + 2) years


man’s present age = (3x2 + 2)years


In three years’ time :


son’s age = (x + 2 + 3) = (x + 5) years


man’s age = (3x2 + 2 + 3)years = (3x2 + 5) years


According to question


Man’s age = 4 son’s age


3x2 + 5 = 4(x + 5)


3x2 + 5 = 4x + 20


3x2 – 4x – 15 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 3 b = – 4 c = – 15


= 3. – 15 = – 45


And either of their sum or difference = b


= – 4


Thus the two terms are – 9 and 5


Difference = – 9 + 5 = – 4


Product = – 9.5 = – 45


3x2 – 9x + 5x – 15 = 0


3x(x – 3) + 5(x – 3) = 0


(x – 3) (3x + 5) = 0


(x – 3) = 0 or (3x + 5) = 0


x = 3 or x = – 5/3 (age cannot be negative)


x = 3


son’s present age = (3 + 2) = 5years


man’s present age = (3.32 + 2) = 29years



Question 43.

A truck covers a distance of 150 km at a certain average speed and then covers another 200 km at an average speed which is 20 km per hour more than the first speed. If the truck covers the total distance in 5 hours, find the first speed of the truck.


Answer:

Let the first speed of the truck be x km/h

Time taken to cover 150 km =


New speed of truck = x + 20 km/h


Time taken to cover 200 km =


According to given question





350x + 3000 = 5(x2 + 20x)


350x + 3000 = 5x2 + 100x


5x2 – 250x – 3000 = 0


x2 – 50x – 600 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 50 c = – 600


= 1. – 600 = – 600


And either of their sum or difference = b


= – 50


Thus the two terms are – 60 and 10


Difference = – 60 + 10 = – 50


Product = – 60.10 = – 600


x2 – 60x + 10x – 600 = 0


x (x – 60) + 10(x – 60) = 0


(x – 60) (x + 10) = 0


x = 60 or x = – 10


x = 60 (speed cannot be negative)


Hence the first speed of the truck is 60 km/hr



Question 44.

While boarding an aeroplane, a passenger got hurt. The pilot showing promptness and concern, made arrangements to hospitalize the injured and so the plane started late by 30 minutes. To reach the destination, 1500 km away, in time, the pilot increased the speed by 100 km/hour. Find the original speed of the plane. Do you appreciate the values shown by the pilot, namely promptness in providing help to the injured and his efforts to reach in time?


Answer:

Let the original speed of the plane be x km/h

Actual speed of the plane = (x + 100) km/h


Distance of journey = 1500km


Time taken to reach destination at original speed =


Time taken to reach destination at actual speed =


According to given question


30 mins = 1/2 hr






x2 + 100x = 300000


x2 + 100x – 300000 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 100 c = – 300000


= 1. – 300000 = – 300000


And either of their sum or difference = b


= 100


Thus the two terms are 600 and – 500


Difference = 600 – 500 = 100


Product = 600. – 500 = – 300000


x2 + 600x – 500x + 300000 = 0


x (x + 600) – 500(x + 600) = 0


(x + 600)(x – 500) = 0


x = – 600 or x = 500


x = 500 (speed cannot be negative)


Hence the original speed of the plane is 500 km/hr



Question 45.

A train covers a distance of 480 km at a uniform speed. If the speed had been 8 km/hr less then it would have taken 3 hours more to cover the same distance. Find the usual speed of the train.


Answer:

Let the usual speed of the train be x km/h

Reduced speed of the train = (x – 8) km/h


Distance of journey = 480km


Time taken to reach destination at usual speed =


Time taken to reach destination at reduced speed =


According to given question


⇒ x2 – 8x = 1280

⇒ x2 – 8x – 1280 = 0

⇒ x2 – 40x + 32x – 1280 = 0

⇒ x(x – 40) + 32(x – 40) = 0

⇒ (x – 40)(x + 32) = 0

⇒ x = 40 or x = – 32

⇒ x = 40 (speed cannot be negative)


Hence the usual speed of the train is 40 km/h


Question 46.

A train travels at a certain average speed for a distance of 54 km and then travels a distance of 63 km at an average speed of 6 km/hr more than the first speed. If it takes 3 hours to complete the total journey, what is its first speed?


Answer:

Let the first speed of the train be x km/h

Time taken to cover 54 km =


New speed of train = x + 6 km/h


Time taken to cover 63 km =


According to given question



Taking LCM

⇒ 117x + 324 = 3(x2 + 6x)

⇒ 117x + 324 = 3x2 + 18x

⇒ 3x2 – 99x – 324 = 0

⇒ x2 – 33x – 108 = 0

⇒ x2 – 36x + 3x – 108 = 0

⇒ x (x – 36) + 3(x – 36) = 0

⇒ (x – 36) (x + 3) = 0

⇒ x = 36 or x = – 3

⇒ x = 36 (speed cannot be negative)

Hence the first speed of the train is 36 km/hr


Question 47.

A train travels 180 km at a uniform speed. If the speed had been 9 km/hr more, it would have taken 1 hour less for the same journey. Find the speed of the train.


Answer:

Let the usual speed of the train be x km/h

Time taken to cover 180 km =


New speed of train = x + 9 km/h


Time taken to cover 180 km =


According to the question






1620 = x2 + 9x


x2 + 9x – 1620 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 9 c = – 1620


= 1. – 1620 = – 1620


And either of their sum or difference = b


= 9


Thus the two terms are 45 and – 36


Difference = – 36 + 45 = 9


Product = – 36.45 = – 1620


x2 + 45x – 36x + 1620 = 0


x(x + 45) – 36(x + 45) = 0


(x + 45) (x – 36) = 0


x = – 45 or x = 36 (but x cannot be negative)


x = 36


Hence the usual speed of the train is 36 km/h



Question 48.

A train covers a distance of 90 km at a uniform speed. Had the speed been 15 km/hr more, it would have taken 30 minutes less for the journey. Find the original speed of the train.


Answer:

Let the original speed of the train be x km/h

Time taken to cover 90 km =


New speed of train = x + 15 km/h


Time taken to cover 90 km =


According to the question






2700 = x2 + 15x


x2 + 15x – 2700 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 15 c = – 2700


= 1. – 2700 = – 2700


And either of their sum or difference = b


= 15


Thus the two terms are – 45 and 60


Difference = 60 – 45 = 15


Product = 60. – 45 = – 2700


x2 + 60x – 45x – 2700 = 0


x(x + 60) – 45(x + 60) = 0


(x + 60) (x – 45) = 0


x = – 60 or x = 45 (but x cannot be negative)


x = 45


Hence the original speed of the train is 45 km/h



Question 49.

A passenger train takes 2 hours less for a journey of 300 km if its speed is increased by 5 km/hr from its usual speed. Find its usual speed.


Answer:

Let the usual speed of the train be x km/h

Time taken to cover 300 km =


New speed of train = x + 5 km/h


Time taken to cover 90 km =


According to the question






750 = x2 + 5x


x2 + 5x – 750 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 5 c = – 750


= 1. – 750 = – 750


And either of their sum or difference = b


= 5


Thus the two terms are – 25 and 30


Difference = 30 – 25 = 5


Product = 30. – 25 = – 750


x2 + 30x – 25x – 750 = 0


x(x + 30) – 25(x + 30) = 0


(x + 30) (x – 25) = 0


x = – 30 or x = 25 (but x cannot be negative)


x = 25


Hence the usual speed of the train is 25 km/h



Question 50.

The distance between Mumbai and Pune is 192 km. Travelling by the Deccan Queen, it takes 48 minutes less than another train. Calculate the speed of the Deccan Queen if the speeds of the two trains differ by 20 km/hr.


Answer:

Let the speed of Deccan Queen be x km/h

Speed of another train = (x – 20)km/h


According to the question




taking LCM




4800 = x2 – 20x cross multiplying


x2 – 20x – 4800 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 20 c = – 4800


= 1. – 4800 = – 4800


And either of their sum or difference = b


= – 20


Thus the two terms are – 80 and 60


Difference = – 80 + 60 = – 20


Product = – 80.60 = – 4800


x2 – 80x + 60x – 4800 = 0


x(x – 80) + 60(x – 80) = 0


(x – 80) (x + 60) = 0


x = 80 or x = – 60 (but x cannot be negative)


Hence the speed of Deccan Queen is 80 km/hr



Question 51.

A motor boat whose speed in still water is 18 km/hr, takes 1 hour more to go 24 km upstream than to return to the same spot. Find the speed of the stream.


Answer:

Let the speed of stream be x km/h

Speed of boat is 18 km/hr

⇒ Speed of boat in downstream = (18 + x)km/h

⇒ Speed of boat in upstream = (18 – x)km/h

As,
distance = spped × time

⇒ Time taken by boat in downstream to travel 24 Km =hours

⇒ Time taken by boat in upstream to travel 24 Km hours

[using (a + b)(a – b) = a2 – b2]

⇒ 324 – x2 = 48x

⇒ x2 + 48x – 324 = 0

⇒ x2 + 54x – 6x – 324 = 0

⇒ x(x + 54) – 6(x + 54) = 0

⇒ (x + 54)(x – 6) = 0

⇒ x = – 54 or x = 6

(but speed cannot be negative)

⇒ x = 6

Hence the speed of stream is 6 km/h


Question 52.

The speed of a boat in still water is 8 km/hr. It can go 15 km upstream and 22 km downstream in 5 hours. Find the speed of the stream.


Answer:

Let the speed of stream be x km/h

Speed of boat is 8 km/hr


Speed downstream = (8 + x)km/h


Speed upstream = (8 – x)km/h






296 – 7x = 320 – 5x2


5x2 – 7x – 24 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 5 b = – 7 c = – 24


= 5. – 24 = – 120


And either of their sum or difference = b


= – 7


Thus the two terms are 8 and – 15


Difference = 8 – 15 = – 7


Product = 8. – 15 = – 120


5x2 – 7x – 24 = 0


5x2 – 15x + 8x – 24 = 0


5x(x – 3) + 8(x – 3) = 0


(5x + 8)(x – 3) = 0


x = 3 or x = – 8/5


(but x cannot be negative)


x = 3


Hence the speed of stream is 3 km/hr



Question 53.

A motorboat whose speed is 9 km/hr in still water, goes 15 km downstream and comes back in a total time of 3 hours 45 minutes. Find the speed of the stream.


Answer:

Let the speed of stream be x km/h

Speed of boat is 9km/hr


Speed downstream = (9 + x)km/h


Speed upstream = (9 – x)km/h


Distance covered downstream = Distance covered upstream = 15km


Total time taken = 3 hours 45 minutes




taking LCM



81 – x2 = 72 cross multiplying


x2 = 81 – 72


x2 = 9 taking square root


x = 3 or – 3 (rejecting negative value)


Hence the speed of stream is 3 km/hr



Question 54.

A takes 10 days less than the time taken by B to finish a piece of work. If both A and B together can finish the work in 12 days, find the time taken by B to finish the work.


Answer:

Let B take x days to complete the work

Work one by B in one day


A will take (x – 10) days to complete the work


Work one by B in one day


According to the question





x2 – 10x = 12 (2x – 10)


x2 – 10x = 24x – 120


x2 – 34x + 120 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 34 c = 120


= 1.120 = 120


And either of their sum or difference = b


= – 34


Thus the two terms are – 30 and – 4


Sum = – 30 – 4 = – 34


Product = – 30. – 4 = 120


x2 – 30x – 4x + 120 = 0


x(x – 30) – 4(x – 30) = 0


(x – 30) (x – 4) = 0


x = 30 or x = 4


x = 30 (number of days to complete the work by B cannot be less than A)


B completes the work in 30 days



Question 55.

Two pipes running together can fill a cistern in minutes. If one pipe takes 3 minutes more than the other to fill it, find the time in which each pipe would fill the cistern.


Answer:

Let one pipe fills a cistern in x mins.

Other pipe fills the cistern in (x + 3) mins.


Running together can fill a cistern in minutes = 40/13 mins


Part filled by one pipe in 1min =


Part filled by other pipe in 1min =


Part filled by both pipes Running together in 1min =





13x2 + 39x = 80x + 120


13x2 – 41x – 120 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 13 b = – 41 c = – 120


= 13. – 120 = – 1560


And either of their sum or difference = b


= – 41


Thus the two terms are – 65 and 24


Difference = – 65 + 24 = – 41


Product = – 65.24 = – 1560


13x2 – 65x + 24x – 120 = 0


13x(x – 5) + 24(x – 5) = 0


(x – 5) (13x + 24) = 0


(x – 5) = 0 (13x + 24) = 0


x = 5 or x = – 24/13


x = 5 (speed cannot be negative fraction)


Hence one pipe fills a cistern in 5 minutes and other pipe fills the cistern in (5 + 3) = 8 minutes.



Question 56.

Two pipes running together can fill a tank in minutes. If one pipe takes 5 minutes more than the other to fill the tank separately, find the time in which each pipe would fill the tank separately.


Answer:

Let the time taken by one pipe to fill the tank be x minutes

The time taken by other pipe to fill the tank = x + 5 minutes


Volume of tank be V


Volume of tank filled by one pipe in x minutes = V


Volume of tank filled by one pipe in 1 minutes = V/x


Volume of tank filled by one pipe in minutes =


Volume of tank filled by other pipe in minutes =


Volume of tank filled by one pipe in minutes + Volume of tank filled by other pipe in minutes = V






200x + 500 = 9x2 + 45x


9x2 – 155x – 500 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 9 b = – 155 c = – 500


= 9. – 500 = – 4500


And either of their sum or difference = b


= – 155


Thus the two terms are – 180 and 25


Difference = – 180 + 25 = – 155


Product = – 180.25 = – 4500


9x2 – 180x + 25x – 500 = 0


9x(x – 20) + 25(x – 20) = 0


(x – 20) (9x + 25) = 0


(x – 20) = 0 (9x + 25) = 0


x = 20 or x = – 25/9


x = 20 (time cannot be negative fraction)


Hence one pipe fills the tank in 20 mins. and other pipe fills the cistern in (20 + 5) = 25 mins



Question 57.

Two water taps together can fill a tank in 6 hours. The tap of larger diameter takes 9 hours less than the smaller one to fill the tank separately. Find the time in which each tap can separately fill the tank.


Answer:

Let the time taken by tap of smaller diameter to fill the tank be x hours

The time taken by tap of larger diameter to fill the tank = x – 9 hours


Let the volume of the tank be V


Volume of tank filled by tap of smaller diameter in x hours = V


⇒ Volume of tank filled by tap of smaller diameter in 1 hour = V/x


⇒ Volume of tank filled by tap of smaller diameter in 6 hours =


Similarly, Volume of tank filled by tap of larger diameter in 6 hours =


Volume of tank filled by tap of smaller diameter in 6 hours + Volume of tank filled by tap of larger diameter in 6 hours = V






⇒ 12x – 54 = x2 – 9x


⇒ x2 – 21x + 54 = 0

⇒ x2 – 18x – 3x + 54 = 0

⇒ x(x – 18) – 3(x – 18) = 0

⇒ (x – 18)(x – 3) = 0
⇒ (x – 18) = 0 and (x – 3) = 0

⇒ x = 18 or x = 3


For x = 3, time taken by tap of larger diameter is negative which is not possible

Thus, x = 18


Hence the time taken by tap of smaller diameter to fill the tank be 18 hours

The time taken by tap of larger diameter to fill the tank = 18 – 9 = 9hours


Question 58.

The length of a rectangle is twice its breadth and its area is 288 cm2. Find the dimensions of the rectangle.


Answer:

Let the length and breadth of a rectangle be 2x and x respectively

According to the question;


Area = 288 cm2


Area = length.breadth


x(2x) = 288 cm2


2x2 = 288


x2 = 144


x = 12 or x = – 12


x = 12 ( x cannot be negative)


length = 2.12 = 24 cm, breadth = 12 cm



Question 59.

The length of a rectangular field is three times its breadth. If the area of the field be 147 sq metres, find the length of the field.


Answer:

Let the length and breadth of a rectangle be 3x and x respectively

According to the question;


Area = 147cm2


Area = length.breadth


x (3x) = 147cm2


3x2 = 147


x2 = 49


x = 7 or x = – 7 taking square root both sides


x = 7 (x cannot be negative)


length = 3.7 = 21cm, breadth = 7cm



Question 60.

The length of a hall is 3 meters more than its breadth. If the area of the hall is 238 sq metres, calculate its length and breadth.


Answer:

Let the breadth of hall be x m

The length of hall will be (x + 3) m


According to the question;


Area = 238cm2


Area = length .breadth


x2 + 3x – 238 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 3 c = – 238


= 1. – 238 = – 238


And either of their sum or difference = b


= 3


Thus the two terms are 17 and – 14


Difference = 17 – 14 = 3


Product = 17. – 14 = – 238


x2 + 17x – 14x – 238 = 0


x(x + 17) – 14(x + 17) = 0


(x + 17) (x – 14) = 0


x = – 17 or x = 14


x = 14 ( x cannot be negative)


Hence the breadth of hall is 14 m and the length of hall is (14 + 3) = 17m



Question 61.

The perimeter of a rectangular plot is 62 m and its area is 228 sq meters. Find the dimensions of the plot.


Answer:

Let the length and breadth of rectangular plot be x and y respectively.

Perimeter = 2(x + y) = 62 – – – – – (1)


Area = xy = 228


y = 228/x


Putting the value of y in 1




taking LCM


x2 + 228 = 31x cross multiplying


x2 – 31x + 288 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = – 31 c = 288


= 1.288 = 288


And either of their sum or difference = b


= – 31


Thus the two terms are – 19 and – 12


Difference = – 19 – 12 = – 31


Product = – 19. – 12 = 288


x2 – 19x – 12x + 288 = 0


x(x – 19) – 12(x – 19) = 0


(x – 19) (x – 12) = 0


x = 19 or x = 12


if x = 19



if x = 12



length is 19m and breadth is 12m


length is 12m and breadth is 19m



Question 62.

A rectangular field is 16 m long and 10 m wide. There is a path of uniform width all around it, having an area of 120 m2. Find the width of the path.


Answer:

Let the width of the path be x m

Length of the field including the path = 16 + x + x = 16 + 2x


Breadth of the field including the path = 10 + x + x = 10 + 2x


Area of field including the path – Area of field excluding the path = Area of path


(16 + 2x) (10 + 2x) – (16.10) = 120


160 + 32x + 20x + 4x2 – 160 = 120


4x2 + 52x – 120 = 0


x2 + 13x – 30 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 13 c = – 30


= 1. – 30 = – 30


And either of their sum or difference = b


= 13


Thus the two terms are 15 and – 2


Difference = 15 – 2 = 13


Product = 15. – 2 = – 30


x2 + 15x – 2x – 30 = 0


x(x + 15) – 2(x + 15) = 0


(x + 15) (x – 2) = 0


x = 2 or x = – 15


x = 2 (width cannot be negative)


Thus the width of the path is 2 m



Question 63.

The sum of the areas of two squares is 640 m2. If the difference in their perimeters be 64 m, find the sides of the two squares.


Answer:

Let the length of first and second square be x and y respectively

According to the question;


x2 + y2 = 640 – – – – (1)


Also 4x – 4y = 64


x – y = 16


x = 16 + y


Putting the value of x in(1) we get


(16 + y)2 + y2 = 640 using (a + b)2 = a2 + 2ab + b2


256 + 32y + y2 + y2 = 640


2y2 + 32y – 384 = 0


y2 + 16y – 192 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 16 c = – 192


= 1. – 192 = – 192


And either of their sum or difference = b


= 16


Thus the two terms are 24 and – 8


Difference = 24 – 8 = 16


Product = 24. – 8 = 192


y2 + 24y – 8y – 192 = 0


y(y + 24) – 8(y + 24) = 0


(y + 24) (y – 8) = 0


(y + 24) = 0 (y – 8) = 0


y = 8 or y = – 24


y = 8 (y cannot be negative)


x = 16 + 8 = 24m


Hence the length of first square is 24m and second square is 8m.



Question 64.

The length of a rectangle is thrice as long as the side of a square. The side of the square is 4 cm more than the width of the rectangle. Their areas being equal, find their dimensions.


Answer:

Let the breadth of a rectangle be x cm

According to the question;


Side of square = (x + 4) cm


Length of a rectangle = [3(x + 4)] cm


Area of rectangle and square are equal – –


3(x + 4)x = (x + 4)2


3x2 + 12x = (x + 4)2


3x2 + 12x = x2 + 8x + 16 { using (a + b)2 = a2 + 2ab + b2}


2x2 + 4x – 16 = 0


x2 + 2x – 8 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 2 c = – 8


= 1. – 8 = – 8


And either of their sum or difference = b


= 2


Thus the two terms are 4 and – 2


Difference = 4 – 2 = 2


Product = 4. – 2 = – 8


x2 + 4x – 2x – 8 = 0


x(x + 4) – 2(x + 4) = 0


(x + 4) (x – 2) = 0


⇒ x = – 4 or x = 2


x = 2 (width cannot be negative)


Thus the breadth of a rectangle = 2 cm


Length of a rectangle = [3(x + 4)] = 3(2 + 4) = 18 cm


Side of square = (x + 4) = 2 + 4 = 6cm



Question 65.

A farmer prepares a rectangular vegetable garden of area 180 sq metres. With 39 metres of barbed wire, he can fence the three sides of the garden, leaving one of the longer sides unfenced. Find the dimensions of the garden.


Answer:

Let the length and breadth of rectangular plot be x and y respectively.

Area = xy = 180 sq m – – – – – (1)


2(x + y) –x = 39


2x + 2y – x = 39


2y + x = 39


x = 39 – 2y


Putting the value of x in (1) we get


(39 – 2y)y = 180


39y – 2y2 = 180


2y2 – 39y + 180 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 2 b = – 39 c = 180


= 2.180 = 360


And either of their sum or difference = b


= – 39


Thus the two terms are – 24 and – 15


Difference = – 24 – 15 = – 39


Product = – 24. – 15 = 360


2y2 – 24y – 15y + 180 = 0


2y(y – 12) – 15(y – 12) = 0


(y – 12)(2y – 15) = 0


y = 12 or y = 15/2 = 7.5


if y = 12 x = 39 – 2y = 39 – (2.12) = 39 – 24 = 15


if y = 7.5 x = 39 – 2y = 39 – [(2)(7.5)] = 39 – 15 = 24


Hence either l = 24 m, b = 7.5 m or l = 15 m, b = 12 m



Question 66.

The area of a right triangle is 600 cm2. If the base of the triangle exceeds the altitude by 10 cm, find the dimensions of the triangle.


Answer:

Let the altitude of the given triangle x cm

Thus the base of the triangle will be (x + 10)cm


Area of triangle =


x (x + 10) = 1200


x2 + 10x – 1200 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 10 c = – 1200


= 1. – 1200 = – 1200


And either of their sum or difference = b


= 10


Thus the two terms are 40 and – 30


Difference = 40 – 30 = 10


Product = 40. – 30 = – 1200


x2 + 40x – 30x – 1200 = 0


x(x + 40) – 30(x + 40) = 0


(x + 40)(x – 30) = 0


x = – 40, 30


x = 30 (altitude cannot be negative)


Thus the altitude of the given triangle is 30cm and base of the triangle = 30 + 10 = 40cm


Hypotenuse2 = altitude2 + base2


Hypotenuse2 = (30)2 + (40)2


= 900 + 1600 = 2500


Hypotenuse = 50 cm


Altitude = 30cm


Base = 40cm



Question 67.

The area of a right – angled triangle is 96 sq metres. If the base is three times the altitude, find the base.


Answer:

Let the altitude of the triangle be x m

The base will be 3x m


Area of triangle = 1/2. Base. altitude


1/2.3x.x = 96



x2 = 64


x = 8 or – 8 taking square root


Value of x cannot be negative


Thus the altitude of the triangle be 8 m


The base will be 3.8 = 24m



Question 68.

The area of a right – angled triangle is 165 sq meters. Determine its base and altitude if the latter exceeds the former by 7 meters.


Answer:

Let the base be x m

The altitude will be x + 7 m


Area of triangle = 1/2 base. altitude


= 1/2 x (x + 7) = 165


x2 + 7x = 330


x2 + 7x – 330 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 7 c = – 330


= 1. – 330 = – 330


And either of their sum or difference = b


= 7


Thus the two terms are 22 and – 15


Difference = 22 – 15 = 7


Product = 22. – 15 = – 330


x2 + 22x – 15x – 330 = 0


x(x + 22) – 15(x + 22) = 0


(x + 22) (x – 15) = 0


x = – 22 or x = 15


Value of x cannot be negative


x = 15


Thus the base be 15m and altitude = 15 + 7 = 22m



Question 69.

The hypotenuse of a right – angled triangle is 20 meters. If the difference between the lengths of the other side’s be 4 meters, find the other sides.


Answer:

Let one side of right – angled triangle be x m and other side be x + 4 m

On applying the Pythagoras theorem –


202 = (x + 4)2 + x2


400 = x2 + 8x + 16 + x2


400 = 2x2 + 8x + 16


2x2 + 8x – 384 = 0


x2 + 4x – 192 = 0


Using the splitting middle term – the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 4 c = – 192


= 1. – 192 = – 192


And either of their sum or difference = b


= 4


Thus the two terms are 16 and – 12


Difference = 16 – 12 = 4


Product = 16. – 12 = – 192


x2 + 16x – 12x – 192 = 0


x(x + 16) – 12(x + 16) = 0


(x + 16) (x – 12) = 0


x = 16 or x = 12


x cannot be negative


Base is 12m and other side is 12 + 4 = 16m



Question 70.

The length of the hypotenuse of a right – angled triangle exceeds the length of the base by 2 cm and exceeds twice the length of the altitude by 1 cm. Find the length of each side of the triangle.


Answer:

Let the base and altitude of the right angled triangle be x and y respectively.

Thus the hypotenuse of triangle will be x + 2 cm


(x + 2)2 = y2 + x2 – – – (1)


Also the hypotenuse exceeds twice the length of the altitude by 1 cm


h = 2y + 1


x + 2 = 2y + 1


x = 2y – 1


Putting the value of x in (1) we get


(2y – 1 + 2)2 = y2 + (2y – 1)2


(2y + 1)2 = y2 + 4 y2 – 4y + 1


4y2 + 4y + 1 = 5y2 – 4y + 1 using (a + b)2 = a2 + 2ab + b2


– y2 + 8y = 0


y(y – 8) = 0


y = 8


x = 16 – 1 = 15cm


h = 16 + 1 = 17cm


Thus the base, altitude, hypotenuse of triangle are 15cm, 8cm, 17cm respectively.



Question 71.

The hypotenuse of a right – angled triangle is 1 metre less than twice the shortest side. If the third side is 1 metre more than the shortest side, find the sides of the triangle.


Answer:

Let the shortest side of triangle be xm

According to the question ;


Hypotenuse = 2x – 1 m


Third side = x + 1 m


Applying Pythagoras theorem


(2x – 1)2 = (x + 1)2 + x2


4x2 – 4x + 1 = x2 + 2x + 1 + x2 using (a – b)2 = a2 – 2ab + b2


2 x2 – 6x = 0


2x (x – 3) = 0


x = 0 or x = 3


Length of side cannot be 0 thus the shortest side is 3m


Hypotenuse = 2x – 1 = 6 – 1 = 5m


Third side = x + 1 = 3 + 1 = 4m


Thus the dimensions of triangle are 3m, 4m and 5m.




Exercise 10f
Question 1.

Which of the following is a quadratic equation?
A. x2 – 3√x + 2 = 0

B. x + 1/x = x2

C. x2 + 1/x2 = 5

D. 2x2 – 5x = (x – 1)2


Answer:

A quadratic equation is of the form i.e. of degree 2 (a ≠ 0, a, b, c are real numbers)


A. this is not of the form hence it is not quadratic equation.


B.




This is not of the form hence it is not quadratic equation.


C.




This is not of the form hence it is not quadratic equation.


D. using






This is of the form i.e. of degree 2 (a ≠ 0, a, b, c are real numbers)


Hence this is a quadratic equation.


Question 2.

Which of the following is a quadratic equation?
A. (x2 + 1) = (2 – x)2 + 3

B. x3 – x2 = (x – 1)3

C. 2x2 + 3 = (5 + x)(2x – 3)

D. none of these


Answer:

A. using





This is not of the form hence it is not quadratic equation.


B. using






This is of the form i.e. of degree 2 (a ≠ 0, a, b, c are real numbers)


Hence this is a quadratic equation.


Question 3.

Which of the following is not a quadratic equation?
A. 3x – x2 = x2 + 5

B. (x + 2)2 = 2(x2 – 5)

C. (√2x + 3)2 = 2x2 + 6

D. (x – 1)2 = 3x2 + x – 2


Answer:

A.




This is a quadratic equation of the form hence i.e. of degree 2 (a ≠ 0, a, b, c are real numbers).


B.


using




This is a quadratic equation of the form i.e. of degree 2 (a ≠ 0, a, b, c are real numbers).


C. using




This is not quadratic since it is not of the form i.e. of degree 2 (a ≠ 0, a, b, c are real numbers).


D.


using




This is a quadratic equation of the form i.e. of degree 2 (a ≠ 0, a, b, c are real numbers).


Question 4.

If x = 3 is a solution of the equation 3x2 + (k – 1)x + 9 = 0 then k = ?
A. 11

B. - 11

C. 13

D. - 13


Answer:


x = 3 is a solution of the equation means it satisfies the equation







Question 5.

If one root of the equation 2x2 + ax + 6 = 0 is 2 then a = ?
A. 7

B. - 7

C.

D.


Answer:

One root of the equation is 2 i.e. it satisfies the equation






Question 6.

The sum of the roots of the equation x2 – 6x + 2 = 0 is
A. 2

B. - 2

C. 6

D. - 6


Answer:

For the equation


comparing with general equation




Where α and β are the roots of the equation.


Question 7.

If the product of the roots of the equation x2 – 3x + k = 10 is - 2 then the value of k is
A. - 2

B. - 8

C. 8

D. 12


Answer:

Given that the product of the roots of the equation is - 2




x2 - 3x + (k - 10) = 0


comparing with general equation


Product of the roots =


=





Question 8.

The ratio of the sum and product of the roots of the equation

7x2 - 12x + 18 = 0 is
A. 7 : 12

B. 7 : 18

C. 3 : 2

D. 2 : 3


Answer:

For the given equation 7x2 - 12x + 18 = 0


a = 7 b = - 12 c = 18 comparing with ax2 + bx + c = 0


Sum of the roots


Product of the roots


Ratio of sum: product =


= 12:18 = 2:3


Question 9.

If one root of the equation 3x2 - 10x + 3 = 0 is 1/3 then the other root is
A.

B.

C. - 3

D. 3


Answer:

For the given equation 3x2 - 10x + 3 = 0


a = 3 b = - 10 c = 3 comparing with ax2 + bx + c = 0


Product of the roots


One root of the equation is


Let other root be




Question 10.

If one root of 5x2 + 13x + k = 0 be the reciprocal of the other root then the value of k is
A. 0

B. 1

C. 2

D. 5


Answer:

Let the roots of equation be than other root will be


Product of two roots =


Product of the roots =


For the given equation 5x2 + 13x + k = 0


a = 5 b = 13 c = k comparing with ax2 + bx + c = 0


Product of the roots


k = 5


Question 11.

If the sum of the roots of the equation kx2 + 2x + 3k = 0 is equal to their product then the value of k is
A.

B.

C.

D.


Answer:

For the given equation kx2 + 2x + 3k = 0


a = k b = 2 c = 3k comparing with ax2 + bx + c = 0


Sum of the roots


Product of the roots


Sum of roots is equal to their product:



Question 12.

The roots of a quadratic equation are 5 and - 2. Then, the equation is
A. x2 - 3x + 10 = 0

B. x2 - 3x - 10 = 0

C. x2 + 3x - 10 = 0

D. x2 + 3x + 10 = 0


Answer:

The roots of a quadratic equation will satisfy the equation - start with option 1


A. x2 - 3x + 10 = 0


For x = 5


52 - (3.5) + 10


25 - 15 + 10 = 20 ≠ 0


Hence this is not the equation


B. x2 - 3x - 10 = 0


For x = 5


52 - (3.5) - 10 = 25 - 15 - 10


= 25 - 25 = 0


For x = - 2


= ( - 2)2 - (3. - 2) - 10


= 4 + 6 - 10 = 10 - 10 = 0


This equation is satisfied for both the roots.


Question 13.

If the sum of the roots of a quadratic equation is 6 and their product is 6, the equation is
A. x2 - 6x + 6 = 0

B. x2 + 6x - 6 = 0

C. x2 - 6x - 6 = 0

D. x2 + 6x + 6 = 0


Answer:

Sum = 6 and Product = 6


Quadratic equation = x2 –Sum x + Product = 0


= x2 - 6x + 6 = 0


Question 14.

If α and β are the roots of the equation 3x2 + 8x + 2 = 0 then = ?
A.

B.

C. - 4

D. 4


Answer:

Given are the roots of the equation 3x2 + 8x + 2 = 0


For the equation a = 3 b = 8 c = 2 comparing with ax2 + bx + c = 0


Sum of roots


Product of roots



Question 15.

The roots of the equation ax2 + bx + c = 0 will be reciprocal of each other if
A. a = b

B. b = c

C. c = a

D. none of these


Answer:

Let the roots of equation be


Product of roots =


Product of the roots


Hence c = a


Question 16.

If the roots of the equation ax2 + bx + c = 0 are equal then c = ?
A.

B.

C.

D.


Answer:

If roots of the equation ax2 + bx + c = 0 are equal


Then D = b2 - 4ac = 0


b2 = 4ac



Question 17.

If the equation 9x2 + 6kx + 4 = 0 has equal roots then k = ?
A. 2 or 0

B. - 2 or 0

C. 2 or - 2

D. 0 only


Answer:

The equation 9x2 + 6kx + 4 = 0 has equal roots


a = 9 b = 6k c = 4


Then D = b2 - 4ac = 0


(6k)2 - 4.9.4 = 0


36k2 = 144


k2 = 4 taking square root both sides


k = 2 or k = - 2


Question 18.

If the equation x2 + 2(k + 2)x + 9k = 0 has equal roots then k = ?
A. 1 or 4

B. - 1 or 4

C. 1 or - 4

D. - 1 or - 4


Answer:

Given that the equation x2 + 2(k + 2)x + 9k = 0 has equal roots.


a = 1 b = 2(k + 2) c = 9k


D = b2 - 4ac = 0


(2k + 4)2 - 4.1.9k = 0


4k2 + 16 + 16k - 36k = 0


4k2 - 20k + 16 = 0


k2 - 5k + 4 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = - 5 c = 4


= 1.4 = 4


And either of their sum or difference = b


= - 5


Thus the two terms are - 4 and - 1


Difference = - 4 - 1 = - 5


Product = - 4. - 1 = 4


k2 - 4k - k + 4 = 0


k(k - 4) - 1(k - 4) = 0


(k - 4) (k - 1) = 0


k = 4 or k = 1


Question 19.

If the equation 4x2 - 3kx + 1 = 0 has equal roots then k = ?
A.

B.

C.

D.


Answer:

Given the equation 4x2 - 3kx + 1 = 0 has equal roots


For the given equation a = 4 b = - 3k c = 1


D = b2 - 4ac = 0


( - 3k)2 - 4.4.1 = 0


9k2 - 16 = 0


9k2 = 16


k2 = 16/9



Question 20.

The roots of ax2 + bx + c = 0, a 0 are real and unequal, if (b2 - 4ac) is
A. > 0

B. = 0

C. < 0

D. none of these


Answer:

The roots of equation are real and unequal, if (b2 - 4ac) > 0


Question 21.

In the equation ax2 + bx + c = 0, it is given that D = (b2 - 4ac) > 0. Then, the roots of the equation are
A. real and equal

B. real and unequal

C. imaginary

D. none of these


Answer:

If for the equation ax2 + bx + c = 0, it is given that D = (b2 - 4ac) > 0 then the roots are real and unequal.


Question 22.

The roots of the equation 2x2 - 6x + 7 = 0 are
A. real, unequal and rational

B. real, unequal and irrational

C. real and equal

D. imaginary


Answer:

For the given equation 2x2 - 6x + 7 = 0


a = 2 b = - 6 c = 7


D = b2 - 4ac


= ( - 6)2 - 4.2.7


= 36 – 56 = - 20 < 0


Thus the roots of equation are imaginary.


Question 23.

The roots of the equation 2x2 - 6x + 3 = 0 are
A. real, unequal and rational

B. real, unequal and irrational

C. real and equal

D. imaginary


Answer:

For the given equation 2x2 - 6x + 3 = 0


a = 2 b = - 6 c = 3


D = b2 - 4ac


= ( - 6)2 - 4.2.3


= 36 - 24 = 12 > 0 this is not a perfect square hence the roots of the equation are real, unequal and irrational


Question 24.

If the roots of 5x2 - kx + 1 = 0 are real and distinct then
A. –2√5 < k < 2√5

B. k > 2 √5 only

C. k < - 2√5 only

D. either k > 2 √5 or k < - 2√5


Answer:

Given that the roots of 5x2 - kx + 1 = 0 are real and distinct


a = 5 b = - k c = 1


D = b2 - 4ac > 0


= ( - k)2 - 4.5.1


= k2 - 20 > 0


k2 > 20


Roots are either


Question 25.

If the equation x2 + 5kx + 16 = 0 has no real roots then
A. k > 8/5

B. k < –8/5

C. –8/5 < k < 8/5

D. none of these


Answer:

Given the equation x2 + 5kx + 16 = 0 has no real


a = 1 b = 5k c = 16


Thus D = b2 - 4ac < 0


= (5k)2 - 4.1.16 < 0


= 25k2 - 64 < 0


25k2 = 64




Question 26.

If the equation x2 - kx + 1 = 0 has no real roots then
A. k < - 2

B. k > 2

C. - 2 < k < 2

D. none of these


Answer:

Given the equation x2 - kx + 1 = 0 has no real roots


a = 1 b = - k c = 1


Thus D = b2 - 4ac < 0


( - k)2 - 4.1.1 < 0


k2 - 4 < 0


k2 < 4


- 2 < k < 2


Question 27.

For what values of k, the equation kx2 - 6x - 2 = 0 has real roots?
A.

B.

C.

D. none of these


Answer:

Given the equation kx2 - 6x - 2 = 0 has real roots


a = k b = - 6 c = - 2


Thus D = b2 - 4ac ≥0


( - 6)2 - 4.k. - 2 ≥0


36 + 8k ≥0


8k≥ - 36



Question 28.

The sum of a number and its reciprocal is . The number is
A.

B.

C.

D.


Answer:

Let the required number be x


According to the question




20x2 - 41x + 20 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 20 b = - 41 c = 20


= 20.20 = 400


And either of their sum or difference = b


= - 41


Thus the two terms are - 25 and - 16


Difference = - 25 - 16 = - 41


Product = - 25. - 16 = 400


20x2 - 25x - 16x + 20 = 0


5x(4x - 5) - 4(4x - 5) = 0


(5x - 4) (4x - 5) = 0



Question 29.

The perimeter of a rectangle is 82 m and its area is 400 m2. The breadth of the rectangle is
A. 25 m

B. 20 m

C. 16 m

D. 9 m


Answer:

Let the length and breadth of the rectangle be l and b respectively


Perimeter of a rectangle is 82 m


2(l + b) = 82


l + b = 41


l = 41 - b - - - - - - (1)


Area is 400 m2


lb = 400


(41 - b) b = 400 using (1)


41b –b2 = 400


b2 - 41b + 400 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = - 41 c = 400


= 1.400 = 400


And either of their sum or difference = b


= - 41


Thus the two terms are - 25 and - 16


Difference = - 25 - 16 = - 41


Product = - 25. - 16 = 400


b2 - 25b - 16b + 400 = 0


b(b - 25) - 16(b - 25) = 0


(b - 25) (b - 16) = 0


b = 25 or b = 16


If b = 25 l = 41 - 25 = 16 but l cannot be less than b


Thus b = 16m


The breadth of the rectangle = 16m


Question 30.

The length of a rectangular field exceeds its breadth by 8 m and the area of the field is 240 m2. The breadth of the field is
A. 20 m

B. 30 m

C. 12 m

D. 16 m


Answer:

Let the breadth of the rectangle be x m


Thus the length of the rectangle is (x + 8) m


Area of the field is 240 m2 = length . breadth


x(x + 8) = 240


x2 + 8x - 240 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = 8 c = - 240


= 1. - 240 = - 240


And either of their sum or difference = b


= 8


Thus the two terms are 20 and - 12


Difference = 20 - 12 = 8


Product = 20. - 12 = - 240


x2 + 20x - 12x - 240 = 0


x(x + 20) - 12(x + 20) = 0


(x + 20) (x - 12) = 0


x = 12 or x = - 20 (but breadth cannot be negative)


The breadth of the rectangle = 12m


Question 31.

The roots of the quadratic equation 2x2 - x - 6 = 0 are
A. - 2, 3/2

B. 2, –3/2

C. - 2, –3/2

D. 2, 3/2


Answer:

2x2 - x - 6 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 2 b = - 1 c = - 6


= 2. - 6 = - 12


And either of their sum or difference = b


= - 1


Thus the two terms are - 4 and 3


Difference = - 4 + 3 = - 1


Product = - 4.3 = - 12


2x2 - 4x + 3x - 6 = 0


2x(x - 2) + 3(x - 2) = 0


(x - 2) (2x + 3) = 0


x = 2 x = - 3/2


Question 32.

The sum of two natural numbers is 8 and their product is 15. Find the numbers.


Answer:

Let the required natural number be x and (8 - x)

their product is 15


x(8 - x) = 15


8x –x2 = 15


x2 - 8x + 15 = 0


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 1 b = - 8 c = 15


= 1.15 = 15


And either of their sum or difference = b


= - 8


Thus the two terms are - 5 and - 3


Sum = - 5 - 3 = - 8


Product = - 5. - 3 = 15


x2 - 5x - 3x + 15 = 0


x(x - 5) - 3(x - 5) = 0


(x - 5) (x - 3) = 0


x = 5 or x = 3


Hence the required natural numbers are 5 and 3



Question 33.

Show that x = - 3 is a solution of x2 + 6x + 9 = 0.


Answer:

If x = - 3 is a solution then it must satisfy the equation

x2 + 6x + 9 = 0


LHS = x2 + 6x + 9


= ( - 3)2 + 6. - 3 + 9


= 9 - 18 + 9


= 18 - 18


= 0 = RHS


Thus x = - 3 is a solution of the equation



Question 34.

Show that x = - 2 is a solution of 3x2 + 13x + 14 = 0.


Answer:

If x = - 2 is a solution then it must satisfy the equation

3x2 + 13x + 14 = 0


LHS = 3x2 + 13x + 14


= 3( - 2)2 + 13( - 2) + 14


= 12 - 26 + 14 = 26 - 26 = 0 = RHS


Thus x = - 2 is a solution of the equation



Question 35.

If is a solution of the quadratic equation 3x2 + 2kx - 3 = 0, find the value of k.


Answer:

Given is a solution of the quadratic equation 3x2 + 2kx - 3 = 0.Thus it must satisfy the equation.




Hence the value of k is



Question 36.

Find the roots of the quadratic equation 2x2 - x - 6 = 0.


Answer:

Given: 2x2 - x - 6 = 0

Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation a = 2 b = - 1 c = - 6


= 2. - 6 = - 12


And either of their sum or difference = b


= - 1


Thus the two terms are - 4 and 3


Sum = - 4 + 3 = - 1


Product = - 4.3 = - 12


2x2 - 4x + 3x - 6 = 0


2x(x - 2) + 3(x - 2) = 0


(x - 2) (2x + 3) = 0


x = 2 or x = - 3/2


Hence the roots of the given equation x = 2 or x =



Question 37.

Find the solution of the quadratic equation 3√3x2 + 10x + √3 = 0


Answer:

The given


Using the splitting middle term - the middle term of the general equation is divided in two such values that:


Product = a.c


For the given equation



And either of their sum or difference = b


= 10


Thus the two terms are 9 and 1


Sum = 9 + 1 = 10


Product = 9.1 = 9


using







Question 38.

If the roots of the quadratic equation 2x2 + 8x + k = 0 are equal then find the value of k.


Answer:

The roots of the quadratic equation 2x2 + 8x + k = 0 are equal then D = 0

a = 2 b = 8 c = k


D = b2 - 4ac = 0


= 82 - 4.2.k = 0


= 64 - 8k = 0


8k = 64


k = 8



Question 39.

If the quadratic equation px2 –2√5px + 15 = 0 has two equal roots then find the value of p.


Answer:

The quadratic equation has two equal roots


D = b2 - 4ac = 0


=


= 20p2 - 60p = 0


= 20p (p - 3) = 0


p = 0 or p = 3


For p = 0 in the equation 0 + 0 + 15 = 0 but this is not possible


Thus p0


p = 3



Question 40.

If 1 is a root of the equation ay2 + ay + 3 = 0 and y2 + y + b = 0 then find the value of ab.


Answer:

Given that y = 1 is a root of the equation ay2 + ay + 3 = 0

a.12 + a.1 + 3 = 0


a + a + 3 = 0


2a + 3 = 0


a = - 3/2


Also y = 1 is a root of the equation y2 + y + b = 0


12 + 1 + b = 0


2 + b = 0


b = - 2



Thus the value of ab = 3



Question 41.

If one zero of the polynomial x2 - 4x + 1 is (2 + √3 ), write the other zero.


Answer:

Given one zero of the polynomial x2 - 4x + 1 is ,

a = 1 b = - 4 c = 1


Than let the other zero of the polynomial be


Sum of zeroes





Hence the other zero of the polynomial is



Question 42.

If one root of the quadratic equation 3x2 - 10x + k = 0 is reciprocal of the other, find the value of k.


Answer:

Let α and β be roots of the quadratic equation 3x2 - 10x + k = 0

a = 3 b = - 10 c = k


Then

For any general quadratic equation in the form ax2 + bx + c = 0, we have
Product of roots

⇒ k = 3


Question 43.

If the roots of the quadratic equation px(x – 2) + 6 = 0 are equal, find the value of p.


Answer:

Given that the roots of the quadratic equation are equal


Comparing with general equation, for the given equation



Hence




4p(p-6) = 0


4p = 0 or (p-6) = 0


p = 0 or p = 6


Putting p = 0 in equation given we get 6 = 0 that is not possible


Hence value of p = 6 for which the equation has equal roots.



Question 44.

Find the values of k so that the quadratic equation x2 – 4kx + k = 0 has equal roots.


Answer:

Given that the quadratic equation has equal roots

Comparing with general equation, for the given equation



Hence







Hence 0 and are values of k for which the equation has equal roots.



Question 45.

Find the values of k for which the quadratic equation 9x2 – 3kx + k = 0 has equal roots.


Answer:

Given that the quadratic equation has equal roots

Comparing with general equation, for the given equation



Hence







Hence 0 and 4 are values of k for which the equation has equal roots.



Question 46.

Solve:


Answer:

Using splitting middle term, the middle term of the general equation is divided in two such values that:

Product = a.c


For the given equation




And either of their sum or difference = b



Thus the two terms are


Difference =


Product =








Hence the roots of given equation are



Question 47.

Solve: 2x2 + ax – a2 = 0


Answer:

Using splitting middle term, the middle term of the general equation is divided in two such values that:

Product = a.c


For the given equation



=


And either of their sum or difference = b


=


Thus the two terms are


Difference =


Product =








Hence roots of equation are



Question 48.

Solve: 3x2 + 5√5x – 10 = 0


Answer:

Using splitting middle term, the middle term of the general equation is divided in two such values that:

Product = a.c


For the given equation



=


And either of their sum or difference = b


=


Thus the two terms are


Difference =


Product = using








Hence roots of equation are



Question 49.

Solve: √3x2 + 10x – 8√3 = 0.


Answer:

Using splitting middle term, the middle term of the general equation is divided in two such values that:

Product = a.c


For the given equation


using


=


And either of their sum or difference = b


=


Thus the two terms are


Difference =


Product =




√3 x(x + 4√3 )-2(x + 4√3) = 0


(√3 x-2)(x + 4√3) = 0




Hence roots of equation are



Question 50.

Solve: √3x2 – 2√2x – 2√3 = 0


Answer:

Using splitting middle term, the middle term of the general equation is divided in two such values that:

Product = a.c


For the given equation


using


=


And either of their sum or difference = b


=


Thus the two terms are


Difference =


Product = = - 6




√3 x(x-√6) + √2(x-√6) = 0


(√3 x + √2)(x-√6) = 0


(√3 x + √2) = 0 or (x-√6) = 0



Hence roots of equation are



Question 51.

Solve: 4√3x2 + 5x –2√3 = 0


Answer:

Using splitting middle term, the middle term of the general equation is divided in two such values that:

Product = a.c


For the given equation



=


And either of their sum or difference = b


=


Thus the two terms are


Difference =


Product =








Hence roots of equation are



Question 52.

Solve: 4x2 + 4bx – (a2 – b2) = 0.


Answer:

Using splitting middle term, the middle term of the general equation is divided in two such values that:

Product = a.c


For the given equation



And either of their sum or difference = b


=


Thus the two terms are


Difference =


=


=


Product =


=


using


=



using



2x[2x + (a + b)] - (a - b)[2x + (a + b)] = 0


[2x - (a - b)][2x + (a + b)] = 0


[2x - (a - b)] = 0 or [2x + (a + b)] = 0


2x = (a - b) or 2x = - (a + b)



Hence roots of equation are



Question 53.

Solve: x2 + 5x – (a2 + a – 6) = 0


Answer:

Using splitting middle term, the middle term of the general equation is divided in two such values that:

Product = a.c


For the given equation a = 1 b = 5 c =


=


And either of their sum or difference = b


=


Thus the two terms are


Difference =


=


Product =


=






x[x + (a + 3)] - (a - 2)[x + (a + 3)] = 0


[x - (a - 2)][x + (a + 3)] = 0


[x - (a - 2)] = 0 or [x + (a + 3)] = 0


x = (a - 2) or x = - (a + 3)


Hence roots of equation are x = (a - 2)or - (a + 3)



Question 54.

x2 + 6x – (a2 + 2a – 8) = 0


Answer:

Using splitting middle term, the middle term of the general equation is divided in two such values that:

Product = a.c


For the given equation


=


And either of their sum or difference = b


=


Thus the two terms are (a + 4) & (a-2)


Difference = (a + 4)-(a-2)


= 6


Product = (a + 4)(a-2)


=






x[x + (a + 4)]-(a-2)[x + (a + 4)] = 0


[x-(a-2)][x + (a + 4)] = 0


[x-(a-2)] = 0 or [x + (a + 4)] = 0


x = (a-2) or x = -(a + 4)


Hence roots of equation are x = (a-2) or-(a + 4)



Question 55.

x2 – 4ax + 4a2 – b2 = 0


Answer:

Using splitting middle term, the middle term of the general equation is divided in two such values that:

Product = a.c


For the given equation


= =


And either of their sum or difference = b


=


Thus the two terms are


Sum =


=


=


Product = using


= =






x[x-(2a + b)]-(2a-b)[x-(2a + b)] = 0


[x-(2a-b)][x-(2a + b)] = 0


[x-(2a-b)] = 0 or [x-(2a + b)] = 0


x = (2a-b) or x = (2a + b)


Hence roots of equation are x = (2a - b) or x = (2a + b)