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Polynomials

Class 10th Mathematics RS Aggarwal Solution
Exercise 2a
  1. x^2 + 7x + 12 Find the zeros of the following quadratic polynomials and verify…
  2. x^2 + 2x - 8 Find the zeros of the following quadratic polynomials and verify…
  3. x^2 + 3x - 10 Find the zeros of the following quadratic polynomials and verify…
  4. 4x^2 - 4x - 3 Find the zeros of the following quadratic polynomials and verify…
  5. 5x^2 - 4 - 8x Find the zeros of the following quadratic polynomials and verify…
  6. 2 root 3x^2 - 5x + root 3 Find the zeros of the following quadratic polynomials…
  7. 2x^2 - 11x + 15 Find the zeros of the following quadratic polynomials and verify…
  8. 4x^2 - 4x + 1 Find the zeros of the following quadratic polynomials and verify…
  9. x^2 - 5 Find the zeros of the following quadratic polynomials and verify the…
  10. 8x^2 - 4 Find the zeros of the following quadratic polynomials and verify the…
  11. 5y^2 + 10y Find the zeros of the following quadratic polynomials and verify the…
  12. 3x^2 - x - 4 Find the zeros of the following quadratic polynomials and verify…
  13. Find the quadratic polynomial whose zeros are 2 and ‒6. Verify the relation…
  14. Find the quadratic polynomial whose zeros are 2/3 -1/4 . Verify the relation…
  15. Find the quadratic polynomial, sum of whose zeros is 8 and their product is 12.…
  16. Find the quadratic polynomial, the sum of whose zeros is 0 and their product is…
  17. Find the quadratic polynomial, the sum of whose zeros is (5/2) and their…
  18. Find the quadratic polynomial, the sum of whose roots is √2 and their product…
  19. If x = 2/3 and x = ‒3 are the roots of the quadratic equation ax^2 + 7x + b = 0…
  20. If (x + a) is a factor of the polynomial 2x^2 + 2ax + 5x + 10, find the value…
  21. One zero of the polynomial 3x^3 + 16x^2 + 15x - 18 is 2/3. Find the other zeros…
Exercise 2b
  1. Verify that 3, ‒2, 1 are the zeros of the cubic polynomial p(x) = x^3 - 2x^2 -…
  2. Verify that 5, -2 and 1/3 are the zeros of the cubic polynomial p(x) = 3x^3 -…
  3. Find a cubic polynomial whose zeros are 2, -3 and 4
  4. Find a cubic polynomial whose zeros are 1/2 , 1 and -3.
  5. Find a cubic polynomial with the sum, sum of the product of its zeros taken two…
  6. f(x) = x^3 - 3x^2 + 5x -3 is divided by g(x) = x^2 - 2. Find the quotient and…
  7. f(x) = x^4 - 3x^2 + 4x + 5 is divided by g(x) = x^2 + 1 - x. Find the quotient…
  8. f(x) = x^4 - 5x + 6 is divided by g(x) = 2 - x^2 . Find the quotient and the…
  9. By actual division, show that x^3 - 3 is a factor 2x^4 + 3x^3 - 2x^2 - 9x - 12.…
  10. On dividing 3x^3 + x^2 + 2x + 5 by a polynomial g(X), the quotient and…
  11. Verify division algorithm for the polynomials f(x) = 8 + 20x + x^2 ‒ 6x^3 and…
  12. It is given that ‒1 is one of the zeros of the polynomial x^3 + 2x^2 ‒ 11x ‒…
  13. If 1 and ‒2 are two zeros of the polynomial (x^3 ‒ 4x^2 ‒ 7x + 10), find its…
  14. If 3 and ‒3 are two zeros of the polynomial (x^4 + x^3 ‒ 11x^2 ‒ 9x + 18), find…
  15. If 2 and ‒2 are two zeros of the polynomial (X^4 + x^3 ‒ 34x^2 ‒ 4x + 120),…
  16. Find all the zeros of (x^4 + x^3 ‒ 23x^2 ‒ 3x + 60), if it is given that two of…
  17. Find all the zeros of (2x^4 ‒ 3x^3 ‒ 5x^2 + 9x ‒ 3), it being given that two of…
  18. Obtain all other zeros of (x^4 + 4x^3 ‒ 2x^2 ‒ 20x ‒15) if two of its zeros are…
  19. Find all the zeros of the polynomial (2x^4 ‒ 11x^3 + 7x^2 + 13x ‒ 7), it being…
Exercise 2c
  1. If one zero of the polynomial x^2 ‒ 4x + 1 is (2 + √3), write the other zero.…
  2. Find the zeros of the polynomial x^2 + x ‒ p (p + 1).
  3. Find the zeros of the polynomial x^2 - 3x - m (m + 3).
  4. Find α, β are the zeros of a polynomial such that α + β= 6 and αβ = 4 then write…
  5. If one zeros of the quadratic polynomial kx^2 + 3x + k is 2 then find the value…
  6. If 3 is a zero of the polynomial 2x^2 + x + k, find the value of k.…
  7. If ‒4 is a zero of the polynomial x^2 ‒ x- (2k + 2) then find the value of k.…
  8. If 1 is a zero of the polynomial ax^2 ‒ 3 (a ‒ 1) x ‒ 1 then find the value of…
  9. If ‒2 is a zero of the polynomial 3x^2 + 4x + 2k then find the value of k.…
  10. Write the zeros of the polynomial x^2 ‒ x ‒ 6.
  11. If the sum of the zeros of the quadratic polynomial kx^2 ‒ 3x + 5 is 1, write…
  12. If the product of the zeros of the quadratic polynomial x^2 ‒ 4x + k is 3 then…
  13. If (x + a) is a factor of (2x2 + 2ax + 5x + 10), find the value of a.…
  14. If (a ‒ b), a and (a + b) are zeros of the polynomial 2x^3 ‒ 6x^2 + 5x - 7,…
  15. If x^3 + x^2 ‒ ax + b is divisible by (x^2 ‒ x), write the values of a and b.…
  16. If α and β are the zeros of the polynomial 2x^2 + 7x + 5, write the value of α…
  17. State division algorithm for polynomials.
  18. The sum of the zeros and the product of zeros of a quadratic polynomial are…
  19. Write the zeros of the quadratic polynomial f(X) = 6x^2 ‒ 3.
  20. Write the zeros of the quadratic polynomial f(x) = 4√3x^2 + 5x ‒ 2√3.…
  21. If α and β are the zeros of the polynomial f(x) = x^2 ‒ 5x + k such that α ‒ β…
  22. If α and β are the zeros of the polynomial f(x) = 6x^2 + x ‒ 2, find the value…
  23. If α and β are the zeros of the polynomial f(x) = 5x^2 ‒ 7x + 1, find the value…
  24. If α and β are the zeros of the polynomial f(x) = x^2 + x - 2, find the value…
  25. If the zeros of the polynomial f(x) = x^3 3x^2 + x + 1 are (a b), a and (a +…
Multiple Choice Questions (mcq)
  1. Which of the following is a polynomial?A. x^2 ‒ 5x + 4√x + 3 B. x3/2 - x + x1/2 + 1 C.…
  2. Which of the following is not a polynomial?A. root 3x^2 - 2 root 3x+5 B. 9x^2 - 4x +…
  3. The zeros of the polynomial x^2 - 2x - 3 areA.‒3, 2 B.‒3, ‒1 C.3, ‒1 D.3, 1…
  4. The zeros of the polynomial x^2 ‒ √2 x - 12 areA. root 2 , - root 2 B. 3 root 2 ,-2…
  5. The zeros of the polynomial 4x^2 + 5√2x - 3 areA. -3 root 2 , root 2 B. -3 root 2 ,…
  6. The zeros of the polynomial x^2 + 1/6 x-2 areA. ‒3, 4 B. -3/2 , 4/3 C. -4/3 , 3/2 D.…
  7. The zeros of the polynomial 7x^2 - 11x/3 - 2/3 areA. 2/3 , -1/7 B. 2/7 , -1/3 C. -2/3 ,…
  8. The sum and the product of the zeros of a quadratic polynomial are 3 and ‒10…
  9. A quadratic polynomial whose zeros are 5 and ‒3, isA. x^2 + 3x + 10 B. x^2 - 2x + 15 C.…
  10. A quadratic polynomial whose zeros are 3/5 -1/2 , isA. 10x^2 + x + 3 B. 10x^2 + x - 3…
  11. The zeros of the quadratic polynomial x^2 + 88x + 125 areA. both positive B. both…
  12. If α and β are the zeros of x^2 + 5x + 8 then the value of (α + β) isA. 5 B. ‒5 C. 8…
  13. If α and β are the zeros of 2x^2 + 5x - 9 then the value of αβ isA. -5/2 B. 5/2 C.…
  14. If one zero of the quadratic polynomial kx^2 + 3x + k is 2 then the value of k isA.…
  15. If one zero of the quadratic polynomial (k - 1) x^2 + kx + 1 is -4 then the value of k…
  16. If -2 and 3 are the zeros of the quadratic polynomial x^2 + (a + 1) x + b thenA. a =…
  17. If one zero of 3x^2 + 8x + k be the reciprocal of the other then k = ?A. 3 B. -3 C.…
  18. If the sum of the zeros of the quadratic polynomial kx^2 + 2x + 3k is equalA. 1/3 B.…
  19. If α, β are the zeros of the polynomial x^2 + 6x + 2 then (1/alpha + 1/beta) = ?A. 3…
  20. If α, β, γ are the zeros of the polynomial x^3 - 6x^2 - x + 30 then (αβ + βγ + γ α) =…
  21. If α, β, γ are the zeros of the polynomial 2x^3 + x^2 - 13x + 6 then αβγ = ?A. ‒3 B. 3…
  22. If α, β, γ be the zeros of the polynomial p(x) such that (α + β + γ) = 3, (αβ + βγ + γ…
  23. If two of the zeros of the cubic polynomial az^3 + bx^2 + cx + d are 0 then in the…
  24. If one of the zeros of the cubic polynomial ax^3 + bx^2 + cx + d is 0 then the product…
  25. If one of the zeros of the cubic polynomial x^3 + ax^2 + bx + c is -1 then the product…
  26. If α, β be the zeros of the polynomial 2x^2 + 5x + k such that alpha^2 + beta^2 +…
  27. One dividing a polynomial p(x) by a nonzero polynomial q(x), let g(x) be the quotient…
  28. Which of the following is a true statement?A. x^2 + 5x - 3 is a linear polynomial B.…
Formative Assessment (unit Test)
  1. Zeros of p(x) = x^2 - 2x - 3 areA. 1, -3 B. 3, -1 C. -3, -1 D. 1, 3…
  2. If α, β, γ are the zeros of the polynomial x^3 - 6x^2 - x + 30 then the value of (αβ +…
  3. If α, β are the zeros of kx^2 - 2x + 3k such that α + β = αβ then k = ?A. 1/3 B. -1/3…
  4. If is given that the difference between the zeros of 4x^2 - 8kx + 9 is 4 and k 0. Then…
  5. Find the zeros of the polynomial x^2 + 2x - 195.
  6. If one zero of the polynomial (a^2 + 9) x^2 + 13x + 6a is the reciprocal of the other,…
  7. Find a quadratic polynomial whose zeros are 2 and ‒5.
  8. If the zeros of the polynomial x^3 - 3x^2 + x + 1 are (a ‒ b), a and (a + b), find the…
  9. Verify that 2 is a zero of the polynomial x^3 + 4x^2 - 3x - 18.
  10. Find the quadratic polynomial, the sum of whose zeros is ‒5 and their products is 6.…
  11. Find a cubic polynomial whose zeros are 3, 5 and ‒2.
  12. Using remainder theorem, find the remainder when p(x) = x^3 + 3x^2 - 5x + 4 is divided…
  13. Show that (x + 2) is a factor of f(x) = x^3 + 4x^2 + x - 6.
  14. If α, β, γ are the zeros of the polynomial p(x) = 6x^3 + 3x^2 - 5x + 1, find the value…
  15. If α, β are the zeros of the polynomial f(x) = x^2 - 5x + k such that α ‒ β = 1, find…
  16. Show that the polynomial f(x) = x^4 + 4x^2 + 6 has no zero.
  17. If one zero of the polynomial p(x) = x^3 - 6x^2 + 11x - 6 is 3, find the other two…
  18. If two zeros of the polynomial p(x) = 2x^4 - 3x^3 - 3x^2 + 6x - 2 are √2 and - √2,…
  19. Find the quotient when p(X) = 3x^4 + 5x^3 - 7x^2 + 2x + 2 is divided by (x^2 + 3x + 1)…
  20. Use remainder theorem to find the value of k, it being given that when x^3 + 2x^2 + kx…

Exercise 2a
Question 1.

Find the zeros of the following quadratic polynomials and verify the relationship between the zeros and the coefficients:

x2 + 7x + 12


Answer:

Let f(x) = x2 + 7x + 12

Put f(x) = 0


x2 + 7x + 12 = 0


x2 + 4x + 3x + 12 = 0


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


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


∴ x = -4 or x = -3


Now,


sum of zeroes = -3 + (-4) = -7=


Product of zeroes = (-3) × (-4)


Hence, relationship verified.



Question 2.

Find the zeros of the following quadratic polynomials and verify the relationship between the zeros and the coefficients:

x2 + 2x – 8


Answer:

Let f(x) = x2 + 2x - 8

Put f(x) = 0


x2 + 2x - 8 = 0


x2 + 2x - 4x - 8 = 0


x(x + 2) – 4 (x + 2) = 0


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


∴ x = 4 or x = -2


Now, sum of zeroes = -2 + 4 = 2 =


Product of zeroes = (4) × (-2)


Hence, relationship verified.


Question 3.

Find the zeros of the following quadratic polynomials and verify the relationship between the zeros and the coefficients:

x2 + 3x – 10


Answer:

Let f(x) = x2 + 3x - 10

Put f(x) = 0


x2 + 3x - 10 = 0


x2 + 5x - 2x - 10 = 0


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


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


∴ x = -5 or x = 2


Now, sum of zeroes = -5 + (2) = -3 =


Product of zeroes = (-5) × (2)


Hence, relationship verified.



Question 4.

Find the zeros of the following quadratic polynomials and verify the relationship between the zeros and the coefficients:

4x2 – 4x – 3


Answer:

Let f(x) = 4x2 - 4x - 3

Put f(x) = 0


4x2 - 4x - 3 = 0


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


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


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



Now, sum of zeroes = 1 =


Product of zeroes


Hence, relationship verified.


Question 5.

Find the zeros of the following quadratic polynomials and verify the relationship between the zeros and the coefficients:

5x2 – 4 – 8x


Answer:

Let f(x) = 5x2 - 4 – 8x

Put f(x) = 0


5x2 - 8x - 4 = 0


5x2 - 10x + 2x - 4 = 0


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


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



Now, sum of zeroes == =


Product of zeroes


Hence, relationship verified.



Question 6.

Find the zeros of the following quadratic polynomials and verify the relationship between the zeros and the coefficients:



Answer:

Let f(x)= 2√3 x2 - 5x + √3

Put f(x) = 0








After rationalizing the denominator, we get,


Now,


sum of zeroes


Product of zeroes


Hence, relationship verified.


Question 7.

Find the zeros of the following quadratic polynomials and verify the relationship between the zeros and the coefficients:

2x2 – 11x + 15


Answer:

Let f(x) = 2x2 – 11x + 15

Put f(x) = 0


2x2 - 11x + 15 = 0


2x2 - 6x - 5x + 15 = 0


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


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



Now, sum of zeroes= =


Product of zeroes


Hence, relationship verified.



Question 8.

Find the zeros of the following quadratic polynomials and verify the relationship between the zeros and the coefficients:

4x2 – 4x + 1


Answer:

Let f(x) =4x2 – 4x + 1 8x

Put f(x) = 0


4x2 - 4x + 1 = 0


(2x)2 – 2(2x)(1) + (1)2 = 0


(2x - 1)2 = 0



Now,


sum of zeroes


Product of zeroes


Hence, relationship verified.



Question 9.

Find the zeros of the following quadratic polynomials and verify the relationship between the zeros and the coefficients:

x2 – 5


Answer:

Let f(x) = x2 – 5

Put f(x) = 0


x2 – 5 = 0


(x – √5) (x + √5) = 0


∴ x = √5 or x = -√5


Now, sum of zeroes


Product of zeroes


Hence, relationship verified.



Question 10.

Find the zeros of the following quadratic polynomials and verify the relationship between the zeros and the coefficients:

8x2 – 4


Answer:

Let f(x) = 8x2 – 4

Put f(x) = 0


8x2 – 4 = 0


(2√2x – 2) (2√2x + 2) = 0



Now, sum of zeroes


Product of zeroes


Hence, relationship verified.



Question 11.

Find the zeros of the following quadratic polynomials and verify the relationship between the zeros and the coefficients:

5y2 + 10y


Answer:

Let f(x) = 5y2 + 10y

Put f(x) = 0


5y2 + 10y = 0


(5y) (y + 2) = 0


∴ x =0 or x = -2


Now, sum of zeroes


Product of zeroes


Hence, relationship verified.



Question 12.

Find the zeros of the following quadratic polynomials and verify the relationship between the zeros and the coefficients:

3x2 – x – 4


Answer:

Let f(x) =3x2 – x – 4

Put f(x) = 0


3x2 - x – 4 = 0


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


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


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



Now, sum of zeroes


Product of zeroes


Hence, relationship verified.



Question 13.

Find the quadratic polynomial whose zeros are 2 and ‒6. Verify the relation between the coefficients and the zeros of the polynomial.


Answer:

Let α = 2 and β = -6

Now, Sum of zeros, α + β = 2 – 6 = -4


And, product of zeroes, αβ = 2(-6) = -12


We know that,


Required polynomial = x2–(α + β) x + αβ


= x2–(- 4)x + (-12)


= x2 + 4x – 12


Now, sum of zeroes =


Product of zeroes =


Hence, relationship verified.



Question 14.

Find the quadratic polynomial whose zeros are . Verify the relation between the coefficients and the zeros of the polynomial.


Answer:


Now, Sum of zeros,


And, product of zeroes,


We know that,


Required polynomial = x2–(α + β)x + αβ




=12x2 – 5x – 2


Now, sum of zeroes


Product of zeroes


Hence, relationship verified.



Question 15.

Find the quadratic polynomial, sum of whose zeros is 8 and their product is 12. Hence, find the zeros of the polynomial


Answer:

Let the zero of the polynomial be α and β

According to the question,


α + β = 8


αβ = 12


∴f(x)= x2 – (α + β)x + (αβ)


=x2 - 8x + 12


∴required polynomial f(x) = x2 - 8x + 12


Put f(x) = 0


x2 - 8x + 12 = 0


x2 - 6x -2x + 12 = 0


x(x – 6) -2(x – 6) = 0


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


x = 6 or x = 2



Question 16.

Find the quadratic polynomial, the sum of whose zeros is 0 and their product is ‒1. Hence, find the zeros of the polynomial.


Answer:

Let the zero of the polynomial be α and β

According to the question,


α + β = 0


αβ = -1


∴f(x)= x2 – (α + β)x + (αβ)


=x2 - 0x - 1


∴required polynomial f(x) = x2 - 1


Put f(x) = 0


x2 - 1 = 0


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


x = 1 or x = -1



Question 17.

Find the quadratic polynomial, the sum of whose zeros is and their product is 1. Hence, find the zeros of the polynomial.


Answer:

Let the zero of the polynomial be α and β

According to the question:

Sum of zeroes:

Product of zeroes:

αβ = 1

we know,
A quadratic equation can be formed using its sum of roots and product of roots with the form

∴f(x)= x2 – (α + β)x + (αβ)



∴ required polynomial f(x)


Put f(x) = 0


x2 –(5/2)x + 1= 0


2x2 – 5x + 2 = 0


2x2 – 4x – x + 2 = 0


2x(x – 2) – 1(x - 2) =0


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


x = 2 or x = 1/2


Question 18.

Find the quadratic polynomial, the sum of whose roots is √2 and their product is 1/3.


Answer:

Let the zero of the polynomial be α and β

According to the question,


α + β = √2



∴ f(x)= x2 – (α + β)x + (αβ)



∴ required polynomial f(x)= x2 - √2 x + 1/3


Put f(x) = 0


x2 - √2 x + 1/3 = 0


3x2 – 3√2x + 1 = 0



Question 19.

If and x = ‒3 are the roots of the quadratic equation ax2 + 7x + b = 0 then find the values of a and b.


Answer:

We have, ax2 + 7x + b = 0

Now, Sum of zeros



∴a = 3 (i)


Product of zeroes (From i)


∴b= -6



Question 20.

If (x + a) is a factor of the polynomial 2x2 + 2ax + 5x + 10, find the value of a.


Answer:

Since, x + a is a factor of 2x2 + 2ax + 5x + 10

∴ x + a = 0


x = -a


Put x = -a in 2x2 + 2ax + 5x + 10 = 0


2(-a)2 + 2a(-a) + 5(-a) + 10 = 0


2a2 – 2a2 – 5a + 10 = 0


-5a = - 10


a = 2



Question 21.

One zero of the polynomial 3x3 + 16x2 + 15x – 18 is 2/3. Find the other zeros of the polynomial.


Answer:

It is given in the question that,

x = 2/3 is one of the zeros of the given polynomial 3x3 + 16x2 + 15x – 18


We have, x = 2/3


x –2/3 = 0


To find the quotient we have to divide the given polynomial by x – 2/3



Quotient = 3x2 + 18x + 27


∴ 3x2 + 18x + 27 = 0


3x2 + 9x + 9x + 27 = 0


3x (x + 3) + 9 (x + 3) = 0


(x + 3) (3x + 9) = 0


(x + 3) = 0 or (3x + 9) = 0


Hence, x = - 3 or x = - 3




Exercise 2b
Question 1.

Verify that 3, ‒2, 1 are the zeros of the cubic polynomial p(x) = x3 – 2x2 – 5x + 6 and verify the relation between its zeros and coefficients.


Answer:

It is given in the question that,

p (x) = x3 – 2x2 – 5x + 6


Also, 3, -2 and 1 are the zeros of the given polynomial


∴ p (3) = (3)3 – 2 (3)2 – 5 (3) + 6


= 27 – 18 – 15 + 6


= 33 – 33


= 0


p (-2) = (-2)3 – 2 (-2)2 – 5 (-2) + 6


= -8 – 8 + 10 + 6


= - 16 + 16


= 0


And, p (1) = (1)3 – 2 (1)2 – 5 (1) + 6


= 1 – 2 – 5 + 6


= 7 – 7


= 0


Verification of the relation is as follows:


Let us assume = 3, = - 2 and = 1


= 3 – 2 + 1


= 2



Also, + + = 3 (-2) + (-2) (1) + 1 (3)


= - 6 – 2 + 3


= - 5



And, = 3 × (-2) × 1


= - 6




Question 2.

Verify that 5, –2 and are the zeros of the cubic polynomial p(x) = 3x3 - 10x2– 27x + 10 and verify the relation between its zeros and coefficients


Answer:

It is given in the question that,

p (x) = 3x3 – 10x2 – 27x + 10


Also, 5, -2 and are the zeros of the given polynomial


∴ p (5) = 3 (5)3 – 10 (5)2 – 27 (5) + 10


= 3 × 125 – 250 – 135 + 10


= 385 – 385


= 0


p (-2) = 3 (-2)3 – 10 (-2)2 – 27 (-2) + 10


= - 24 – 40 + 54 + 10


= - 64 + 64


= 0


And, p () = 3 ()3 – 10 ()2 – 21 () + 10




=


=


= 0


Verification of the relation is as follows:


Let us assume α = 5, β = - 2 and γ = 1/3


α + β + γ = 5 – 2 + 1/3 =



Also, + + = 5 (-2) + (-2) () + () (5)


= - 27/3


= - 9



And, αβγ =



Hence, verified



Question 3.

Find a cubic polynomial whose zeros are 2, –3 and 4


Answer:

Let the zeros of the polynomial be a, b and c

Where a = 2, b = - 3 and c = 4


The cubic polynomial can be calculated as follows:


x3 – (a + b + c) x2 + (ab + bc + ca)x – abc


Putting the values of a, b and c in the above equation we get:


= x3 – (2 – 3 + 4) x2 + (-6 – 12 + 8) x – (- 24)


= x3 – 3x2 – 10x + 24



Question 4.

Find a cubic polynomial whose zeros are , 1 and –3.


Answer:

Let the zeros of the polynomial be a, b and c

Where a = 1/2, b = 1 and c = - 3


The cubic polynomial can be calculated as follows:


x3 – (a + b + c) x2 + (ab + bc + ca) x – abc


Putting the values of a, b and c in the above equation we get:


= x3 – (1/2 + 1 - 3) x2 + (1/2 – 3 – 3/2)x – (- 3/2)


= x3 – (-3/2) x2 – 4x + 3/2


= 2x3 + 3x2 – 8x + 3



Question 5.

Find a cubic polynomial with the sum, sum of the product of its zeros taken two at a time, and the product of its zeros as 5, –2 and –24 respectively.


Answer:

The required cubic polynomial can be calculated as:

x3 – (Sum of the zeros) x2 + (Sum of the product of the zeros taking two at a time) x – Product of Zeros


It is given that, sum of the product of its zeros taken two at a time, and the product of its zeros as 5, –2 and –24 respectively


Putting these values in the equation, we get:


x3 – 5x2 – 2x + 24


Question 6.

Find the quotient and the remainder when:

f(x) = x3 – 3x2 + 5x –3 is divided by g(x) = x2 – 2.


Answer:

It is given in the question that,

f (x) = x3 – 3x2 + 5x – 3


And, g (x) = x2 – 2



Hence,


Quotient q (x) = x – 3


Remainder r (x) = 7x – 9



Question 7.

Find the quotient and the remainder when:

f(x) = x4 – 3x2 + 4x + 5 is divided by g(x) = x2 + 1 – x.


Answer:

It is given in the question that,

f (x) = x4 – 3x2 + 4x + 5


And, g (x) = x2 + 1 – x



Hence,


Quotient q (x) = x2 + x - 3


Remainder r (x) = 8



Question 8.

Find the quotient and the remainder when:

f(x) = x4 – 5x + 6 is divided by g(x) = 2 – x2.


Answer:

It is given in the question that,

f (x) = x4 – 5x + 6 = x4 + 0x3 + 0x2 – 5x + 6


And, g (x) = x2 + 1 – x



Hence,


Quotient q (x) = x2 – 2


Remainder r (x) = 5x + 10



Question 9.

By actual division, show that x3 – 3 is a factor 2x4 + 3x3 – 2x2 – 9x – 12.


Answer:

It is given in the question that,

f (x) = 2x4 + 3x3 – 2x2 – 9x – 12


And, g (x) = x3 – 3



Hence,


Quotient q (x) = 2x2 + 3x + 4


Remainder r (x) = 0


As the remainder is 0


∴ x2 – 3 is a factor of 2x4 + 3x3 – 2x2 – 9x – 12



Question 10.

On dividing 3x3 + x2 + 2x + 5 by a polynomial g(X), the quotient and remainder are (3x – 5) and (9x + 10) respectively. Find g(x).


Answer:

We know that,

According to the division rule, we have


Dividend = Quotient × Divisor + Remainder


Here, we have:


Dividend = 3x3 + x2 + 2x + 5


Quotient = 3x – 5


Remainder = 9x + 10


Putting these values in the formula, we get


3x3 + x2 + 2x + 5 = 3x – 5 × g (x) + 9x + 10


3x3 + x2 + 2x + 5 – 9x – 10 = (3x – 5) × g(x)


3x3 + x2 – 7x – 5 = (3x – 5) × g (x)


g (x) =



∴ g (x) = x2 + 2x + 1



Question 11.

Verify division algorithm for the polynomials f(x) = 8 + 20x + x2 ‒ 6x3 and g(x) = 2 + 5x ‒ 3x2.


Answer:

It is given in the question that,

f (x) = - 6x3 + x2 + 20x + 8


g (x) = - 3x2 + 5x + 2



∴ Quotient = 2x + 3


Remainder = x + 2


We know that, according to division rule:


Dividend = Quotient × Divisor + Remainder


Putting the values in the above formula, we get:


- 6x3 + x2 + 20x + 8 = (- 3x2 + 5x + 2) (2x + 3) + (x + 2)


-6x3 + x2 + 20x + 8 = - 6x3 + 10x2 + 4x – 9x2 + 15x + 6 + x + 2


-6x3 + x2 + 20x + 8 = -6x3 + x2 + 20x + 8


Question 12.

It is given that ‒1 is one of the zeros of the polynomial x3 + 2x2 ‒ 11x ‒ 12. Find all the zeros of the given polynomial.


Answer:

Let us assume f (x) = x3 + 2x2 ‒ 11x ‒ 12

It is given in the question that, -1 is a zero of the polynomial


∴ (x + 1) is a factor of f (x)


Now on dividing f (x) by (x + 1), we get



f (x) = x3 + 2x2 ‒ 11x ‒ 12


= (x + 1) (x2 + x – 12)


= (x + 1) {x2 + 4x – 3x – 12}


= (x + 1) {x (x + 4) – 3 (x + 4)}


= (x + 1) (x – 3) (x + 4)


∴ f (x) = 0


(x + 1) (x – 3) (x + 4) = 0


(x + 1) = 0 0r (x – 3) = 0 or (x + 4) = 0


x = -1 or x = 3 or x = - 4


Hence, zeros of the polynomial are -1, 3 and -4



Question 13.

If 1 and ‒2 are two zeros of the polynomial (x3 ‒ 4x2 ‒ 7x + 10), find its third zero.


Answer:

Let us assume f (x) = x3 – 4x2 – 7x + 10

As 1 and – 2 are the zeros of the given polynomial therefore each one of (x – 1) and (x + 2) is a factor of f (x)


Consequently, (x – 1) (x + 2) = (x2 + x – 2) is a factor of f (x)


Now, on dividing f (x) by (x2 + x – 2) we get:



f (x) = 0


(x2 + x – 2) (x – 5) = 0


(x – 1) (x + 2) (x – 5) = 0


∴ x = 1 or x = - 2 or x = 5


Hence, the third zero is 5



Question 14.

If 3 and ‒3 are two zeros of the polynomial (x4 + x3 ‒ 11x2 ‒ 9x + 18), find all the zeros of the given polynomial.


Answer:

Let us assume f (x) = x4 + x3 ‒ 11x2 ‒ 9x + 18

As 3 and – 3 are the zeros of the given polynomial therefore each one of (x + 3) and (x - 3) is a factor of f (x)


Consequently, (x – 3) (x + 3) = (x2 – 9) is a factor of f (x)


Now, on dividing f (x) by (x2 – 9) we get:



f (x) = 0


(x2 + x – 2) (x2 – 9) = 0


(x – 1) (x + 2) (x – 3) (x + 3) = 0


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


Hence, all the zeros of the given polynomial are 1, -2, 3 and -3



Question 15.

If 2 and ‒2 are two zeros of the polynomial (X4 + x3 ‒ 34x2 ‒ 4x + 120), find all the zeros of the given polynomial.


Answer:

Let us assume f (x) = x4 + x3 ‒ 34x2 ‒ 4x + 120

As 2 and – 2 are the zeros of the given polynomial therefore each one of (x - 2) and (x + 2) is a factor of f (x)


Consequently, (x – 2) (x + 2) = (x2 – 4) is a factor of f (x)


Now, on dividing f (x) by (x2 – 4) we get:



f (x) = 0


(x2 + x – 30) (x2 – 4) = 0


(x2 + 6x – 5x – 30) (x – 2) (x + 2)


[x (x + 6) – 5 (x + 6)] (x – 2) (x + 2)


(x – 5) (x + 6) (x – 2) (x + 2) = 0


∴ x = 5 or x = - 6 or x = 2 or x = - 2


Hence, all the zeros of the given polynomial are 2, -2, 5 and -6


Question 16.

Find all the zeros of (x4 + x3 ‒ 23x2 ‒ 3x + 60), if it is given that two of its zeros are √3 and ‒√3.


Answer:

Let us assume f (x) = x4 + x3 ‒ 23x2 ‒ 3x + 60

As √3 and –√3 are the zeros of the given polynomial therefore each one of (x - √3) and (x - √3) is a factor of f (x)


Consequently, (x – √3) (x + √3) = (x2 – 3) is a factor of f(x)


Now, on dividing f (x) by (x2 – 3) we get:



f (x) = 0


(x2 + x – 20) (x2 – 3) = 0


(x2 + 5x – 4x – 20) (x2 – 3)


[x (x + 5) – 4 (x + 5)] (x2 – 3)


(x – 4) (x + 5) (x – ) (x + ) = 0


∴ x = 4 or x = - 5 or x = or x = -


Hence, all the zeros of the given polynomial are , -, 4 and - 5



Question 17.

Find all the zeros of (2x4 ‒ 3x3 ‒ 5x2 + 9x ‒ 3), it being given that two of its zeros are √3 and – √3.


Answer:

Let us assume f (x) = 2x4 - 3x3 ‒ 5x2 + 9x - 3

As and – are the zeros of the given polynomial therefore each one of (x - ) and (x + ) is a factor of f (x)


Consequently, (x – ) (x + ) = (x2 – 3) is a factor of f (x)


Now, on dividing f (x) by (x2 – 3) we get:



f (x) = 0


2x2 - 3x2 – 5x2 + 9x - 3 = 0


(x2 – 3) (2x2 – 3x + 1) = 0


(x2 - 3) (2x2 – 2x – x + 1) (2x – 1) (x - 1) = 0


(x – ) (x + ) (2x – 1) (x - 1) = 0


∴ x = or x = - or x = or x = 1


Hence, all the zeros of the given polynomial are , -, and 1



Question 18.

Obtain all other zeros of (x4 + 4x3 ‒ 2x2 ‒ 20x ‒15) if two of its zeros are √5 and – √5.


Answer:

Let us assume f (x) = x4 + 4x3 ‒ 2x2 ‒ 20x - 15

As (x-√5) and (x-√5) are the zeros of the given polynomial therefore each one of (x-√5) and (x + √5) is a factor of f (x)


Consequently, (x-√5) (x + √5) = (x2 – 5) is a factor of f (x)


Now, on dividing f (x) by (x2 – 5) we get:



f (x) = 0


x4 + 4x3 – 7x2 – 20x – 15 = 0


(x2 – 5) (x2 + 4x + 3) = 0


(x -√5) (x + √5) (x + 1) (x + 3) = 0


∴ x = √5 or x = - √5 or x = - 1 or x = - 3


Hence, all the zeros of the given polynomial are √5, -√5, - 1 and - 3



Question 19.

Find all the zeros of the polynomial (2x4 ‒ 11x3 + 7x2 + 13x ‒ 7), it being given that two of its zeros are (3 + √3) and (3 ‒ √3)


Answer:

Let us assume f (x) = 2x4 – 11x3 + 7x2 + 13x - 7

As (3 + √2) and (3- √2) are the zeros of the given polynomial therefore each one of (x + 3 + √2) and (x + 3 - √2) is a factor of f (x)


Consequently, [(x – (3 + √2)][(x – (3 -√2)


= [(x – 3) - √2] [(x – 3) + √2]


= [(x – 3)2 – 2] = x2 – 6x + 7 is a factor of f (x)


Now, on dividing f (x) by (x2 – 6x + 7) we get:



f (x) = 0


2x4 - 11x3 + 7x2 + 13x – 7 = 0


(x2 - 6x + 7) (2x2 + x – 1) = 0


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


∴ x = - 3 - √2 or x = - 3 + √2 or x = 1/2 or x = - 1


Hence, all the zeros of the given polynomial are (-3 -√2), (-3 + √2), 1/2 and – 1



Exercise 2c
Question 1.

If one zero of the polynomial x2 ‒ 4x + 1 is (2 + √3), write the other zero.


Answer:

It is given in the question that, zero of the polynomial x2 – 4x + 1 is (2 + )

Let the other zero of the polynomial be a


We know that,


Sum of zeros =


∴ 2 + √3 + a =


a = 2 - √3


Hence, the other zero of the given polynomial is (2 -√3)



Question 2.

Find the zeros of the polynomial x2 + x ‒ p (p + 1).


Answer:

We have,

f (x) = x2 + x – p (p + 1)


f (x) = x2 + (p + 1 - p)x – p (p + 1)

= x2 + (p + 1) x – px – p (p + 1)

= x [x + (p + 1)] – p [x + (p + 1)]

= [x + (p + 1)] (x – p)


To find the zeroes of f(x), let f (x) = 0


[x + (p + 1)] (x – p) = 0


[x + (p + 1)] = 0 or (x – p) = 0


x = p or x = - (p + 1)


Hence, the zeros of the given polynomial are p and – (p + 1)


Question 3.

Find the zeros of the polynomial x2 – 3x – m (m + 3).


Answer:

We have,

f (x) = x2 – 3x – m (m + 3)


Now, by adding and subtracting px, we get


f (x) = x2 - mx - 3x + mx – m (m + 3)


= x [x – (m + 3)] + m [x – (m + 3)]


= [x - (m + 3)] (x + m)


∴ f (x) = 0


[x - (m + 3)] (x + m) = 0


[x - (m + 3)] = 0 or (x + m) = 0


x = m + 3 or x = - m


Hence, the zeros of the given polynomial are - m and m + 3



Question 4.

Find α, β are the zeros of a polynomial such that α + β= 6 and αβ = 4 then write the polynomial.


Answer:

It is given in the question that,

α + β= 6


And, αβ = 4


We know that,


If the zeros of the polynomial are then the quadratic polynomial can be found as x2 – () x + (i)


Now substituting the values in (i), we get


x2 – 6x + 4



Question 5.

If one zeros of the quadratic polynomial kx2 + 3x + k is 2 then find the value of k.


Answer:

It is given in the question that,

One of the zero of the polynomial kx2 + 3x + k is 2


∴ It will satisfy the above polynomial


Now, we have


k (2)2 + 3 (2) + k = 0


4k + 6 + k = 0


5k + 6 = 0


5k = - 6


∴ k = -6/5



Question 6.

If 3 is a zero of the polynomial 2x2+ x + k, find the value of k.


Answer:

It is given in the question that,

One of the zero of the polynomial 2x2 + x + k is 3


∴ It will satisfy the above polynomial


Now, we have


2 (3)2 + 3 + k = 0


21 + k = 0


k = - 21



Question 7.

If ‒4 is a zero of the polynomial x2 ‒ x- (2k + 2) then find the value of k.


Answer:

It is given in the question that,

One of the zero of the polynomial x2 – x- (2k + 2) is - 4


∴ It will satisfy the above polynomial


Now, we have


(- 4)2 – (- 4) - (2k + 2) = 0


16 + 4 - 2k - 2 = 0


- 2k = - 18


k = 18/2


∴ k = 9


Question 8.

If 1 is a zero of the polynomial ax2 ‒ 3 (a ‒ 1) x ‒ 1 then find the value of a.


Answer:

It is given in the question that,

One of the zero of the polynomial ax2 – 3 (a – 1) x - 1 is 1


∴ It will satisfy the above polynomial


Now, we have

a (1)2 – 3(a – 1) 1 – 1 = 0

a – 3a + 3 - 1 = 0

- 2a = - 2

∴ a = 1


Question 9.

If ‒2 is a zero of the polynomial 3x2 + 4x + 2k then find the value of k.


Answer:

It is given in the question that,

One of the zero of the polynomial 3x2 + 4x + 2k is - 2


∴ It will satisfy the above polynomial


Now, we have


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


12 - 8 + 2k = 0


4 + 2k = 0


2k = - 4


∴ k = - 2



Question 10.

Write the zeros of the polynomial x2 ‒ x ‒ 6.


Answer:

We have,

f (x) = x2 – x – 6


= x2 – 3x + 2x – 6


= x (x – 3) + 2 (x – 3)


= (x – 3) (x + 2)


f (x) = 0


(x – 3) (x – 2) = 0


(x – 3) = 0 or (x – 2) = 0


x = 3 or x = 2


∴ The zeros of the given polynomial are 3 and – 2



Question 11.

If the sum of the zeros of the quadratic polynomial kx2 ‒ 3x + 5 is 1, write the value of k.


Answer:

It is given in the question that, zero of the polynomial kx2 – 3x + 5 is 1

Now by using the relationship between the zeros of the quadratic polynomial we have:


Sum of zeros =



⇒ k = 3



Question 12.

If the product of the zeros of the quadratic polynomial x2 ‒ 4x + k is 3 then write the value of k.


Answer:

It is given in the question that, zero of the polynomial x2 – 4x + k is 3

Now by using the relationship between the zeros of the quadratic polynomial we have:


Sum of zeros =


3 = k/1


k = 3



Question 13.

If (x + a) is a factor of (2x2 + 2ax + 5x + 10), find the value of a.


Answer:

It is given in the question that,

(x + 4) is a factor of 2x2 + 2ax + 5x + 10


Now, we have


x + a = 0


x = - a


As (x + a) is a factor of 2x2 + 2ax + 5x + 10


Thus, it will satisfy the given polynomial


∴ 2 (- a)2 + 2a (- a) + 5 (- a) + 10 = 0


- 5a + 10 = 0


a = 2



Question 14.

If (a ‒ b), a and (a + b) are zeros of the polynomial 2x3 ‒ 6x2 + 5x – 7, write the value of a.


Answer:

It is given in the question that, zero of the polynomial 2x3 – 6x2 + 5x - 7 is (a – b), a and (a + b)

Now by using the relationship between the zeros of the quadratic polynomial we have:


Sum of zeros =


a – b + a + a + b = (- (-6))/2


3a = 3


a = 1



Question 15.

If x3 + x2 ‒ ax + b is divisible by (x2 ‒ x), write the values of a and b.


Answer:

Firstly, equating x2 – x to 0 to find the zeros we get:

x (x – 1) = 0


x = 0 or x – 1 = 0


x = 0 or x = 1


As x3 + x2 – ax + b is divisible by x2 – x


∴ The zeros o x2 – x will satisfy x3 + x2 – ax + b


Hence, (0)3 + 02 – a (0) + b = 0


b = 0


Also,


(1)3 + 12 – a (1) + 0 = 0


∴ a = 2



Question 16.

If α and β are the zeros of the polynomial 2x2 + 7x + 5, write the value of α + β + αβ.


Answer:

It is given in the question that, zeros of the polynomial 2x2 + 7x + 5 are

Now by using the relationship between the zeros of the quadratic polynomial we have:


Sum of zeros = and product of zeros =


= and




Question 17.

State division algorithm for polynomials.


Answer:

The Division algorithm for polynomials is as follows:

If we have two polynomials f (x) and g (x) and the degree of f (x) is greater than the degree of g (x), where g (x) 0 than there exist two unique polynomials q (x) and r (x) such that:


f (x) = g (x)× q(x) + r(x)


where r (x) – 0 or degree of r (x) < degree of g (x)



Question 18.

The sum of the zeros and the product of zeros of a quadratic polynomial are -1/2 and ‒3 respectively. Write the polynomial.


Answer:

We know that,

We can find the quadratic polynomial if we know the sum of the roots and product of the roots by using the formula:


x2 – (Sum of the zeroes)x + Product of zeros


∴ x2 – (-1/2) x + (- 3)



∴ The required polynomial is x2 + - 3



Question 19.

Write the zeros of the quadratic polynomial f(X) = 6x2 ‒ 3.


Answer:

We know that,

To find the zeros of the quadratic polynomial we have to equate the f (x) to 0


∴ f (x) = 0


6x2 – 3 = 0


3 (2x2 – 1) = 0


2x2 – 1 = 0


2x2 = 1


x2 = 1/2


x = � 1/√2


Hence, the zeros of the quadratic polynomial f (x) are 1/√2 and -1/√2



Question 20.

Write the zeros of the quadratic polynomial f(x) = 4√3x2 + 5x ‒ 2√3.


Answer:

We know that,

To find the zeros of the quadratic polynomial we have to equate the f (x) to 0


∴ f (x) = 0


4√3 x2 + 5x - 2√3 = 0


4√3 x2 + 8x – 3x - 2√3 = 0


4x (√3 x + 2) - √3 (√3 x + 2) = 0


(√3 x + 2) = 0 or (4x - √3) = 0


x =- or x =


Hence, the zeros of the quadratic polynomial f (x) are - or



Question 21.

If α and β are the zeros of the polynomial f(x) = x2 ‒ 5x + k such that α ‒ β = 1, find the value of k.


Answer:

It is given in the question that,

Zeros of the polynomial x2 – 5x + k are


Also,


α- β = 1


Now by using the relationship between the zeros of the quadratic polynomial we have:


Sum of zeros = and product of zeros =


and


α + β=5 and α β = k/1


Now solving α- β=1 and α + β = 5, we get:


= 2


these values in we get:




Question 22.

If α and β are the zeros of the polynomial f(x) = 6x2 + x ‒ 2, find the value of


Answer:

It is given in the question that,

Zeros of the polynomial 6x2 + x - 2 are


Now by using the relationship between the zeros of the quadratic polynomial we have:


Sum of zeros = and product of zeros =


= and


Now we have:



=


=


=


=


=



Question 23.

If α and β are the zeros of the polynomial f(x) = 5x2 ‒ 7x + 1, find the value of


Answer:

It is given in the question that,

Zeros of the polynomial 5x2 – 7x + 1 are


Now by using the relationship between the zeros of the quadratic polynomial we have:


Sum of zeros = and product of zeros =


= and


= and


Now, we have:


=


=


= 7



Question 24.

If α and β are the zeros of the polynomial f(x) = x2 + x – 2, find the value of


Answer:

It is given in the question that,

Zeros of the polynomial x2 + x - 2 are


Now by using the relationship between the zeros of the quadratic polynomial we have:


Sum of zeros = and product of zeros =


= and


= - 1 and


Now, we have:


= ()2


=


=


=


=



() =



Question 25.

If the zeros of the polynomial f(x) = x3 – 3x2 + x + 1 are (a – b), a and (a + b), find the a and b.


Answer:

It is given in the question that,

Zeros of the polynomial x3 – 3x2 + x + 1 are (a – b), a and (a + b)


Now by using the relationship between the zeros of the quadratic polynomial we have:


Sum of zeros =


a – b + a + a + b =


3a = 3


a =


Now, we have product of zeros =


(a – b) (a) (a + b) =


(1 – b) (1) (1 + b) = - 1


1 – b2 = - 1


b2 = 2


∴ b =




Multiple Choice Questions (mcq)
Question 1.

Which of the following is a polynomial?
A. x2 ‒ 5x + 4√x + 3

B. x3/2 – x + x1/2 + 1

C.

D.


Answer:

We know that, Polynomial is an expression consist of constants, variables and exponents which are connected by addition, subtraction, multiplication and division but the exponent of variables cannot be in fraction and has to be a positive integer.


Hence, option D is correct.


Question 2.

Which of the following is not a polynomial?
A.

B.

C.

D.


Answer:

We can observe that in the second expression the power of x is -1 but we know that the exponent of the variable in a polynomial has to be a positive term.


Hence, option D is correct.


Question 3.

The zeros of the polynomial x2 – 2x – 3 are
A.‒3, 2

B.‒3, ‒1

C.3, ‒1

D.3, 1


Answer:

We have, f(x) = x2 – 2x – 3


Now, put f(x) = 0


x2 – 2x – 3 = 0


x2 – 3x + x – 3 = 0


x(x – 3) + 1(x – 3) = 0


(x – 3)(x + 1) = 0


Thus, x = 3, -1


Hence, option C is correct.


Question 4.

The zeros of the polynomial x2 ‒ √2 x – 12 are
A.

B.

C.

D.


Answer:

We have, f(x) = x2 ‒ √2x – 12


Now, put f(x) = 0


x2 ‒ √2x – 12 = 0

x2 - 3√2x + 2√2x - 12 = 0

x(x ‒ 3√2) + 2√2(x – 3√2)=0

(x ‒ 3√2) + (x + 2√2) = 0

Thus, x= 3√2 , -2√2


Hence option B is correct.


Question 5.

The zeros of the polynomial 4x2 + 5√2x – 3 are
A.

B.

C.

D. None of these


Answer:

We have, f(x) = 4x2 + 5 x – 3


Now, put f(x) = 0


4x2 + 5 x – 3 = 0


4x2 + x -√2x – 3 = 0


2√2x(√2x + 3) -1(√2x + 3) = 0


(2√2x -1) (√2x + 3) = 0



Hence, option C is correct.


Question 6.

The zeros of the polynomial are
A. ‒3, 4

B.

C.

D. None of these


Answer:

We have, f(x) = x2 + x – 2


f(x) = 6x2 + x – 12 =0


Now, put f(x) = 0


6x2 + x – 12 = 0


6x2 + 9x – 8x – 12 = 0


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



Hence, option B is correct.


Question 7.

The zeros of the polynomial are
A.

B.

C.

D. None of these


Answer:


f(x) = 21x2 – 11x – 2 =0


Now, put f(x) = 0


21x2 – 11x – 2 =0


21x2 – 14x + 3x – 2 =0


7x(3x – 2) + 1 (3x – 2) = 0


(3x – 2) (7x + 1) = 0



Hence, option A is correct.


Question 8.

The sum and the product of the zeros of a quadratic polynomial are 3 and ‒10 respectively. The quadratic polynomial is
A. x2 – 3x + 10

B. x2 + 3x – 10

C. x2 – 3x – 10

D. x2 + 3x + 10


Answer:

We have, sum of zeroes(α + β) = 3


Product of zeroes(αβ) = -10


We know that,


Required polynomial = x2 – (α + β) + αβ


= x2 – 3x – 10


Hence, option C is correct.


Question 9.

A quadratic polynomial whose zeros are 5 and ‒3, is
A. x2 + 3x + 10

B. x2 – 2x + 15

C. x2 – 2x – 15

D. none of these


Answer:

We have, α = 5, β = -3


Thus, sum of zeros(α + β) = 5 – 3 = 2


Product of zeros(αβ) = 5(-3) = -15


We know that,


Required polynomial = x2 – (α + β) + αβ


= x2 – 2x – 15


Hence, option C is correct.


Question 10.

A quadratic polynomial whose zeros are , is
A. 10x2 + x + 3

B. 10x2 + x – 3

C. 10x2 – x + 3

D. 10x2 – x – 3


Answer:


Thus, sum of zeros(α + β)




We know that,


Required polynomial = x2 – (α + β) + αβ



Hence, option D is correct.


Question 11.

The zeros of the quadratic polynomial x2 + 88x + 125 are
A. both positive

B. both negative

C. one positive and one negative

D. both equal


Answer:

Let the zeros be α and β


We know that, α + β = -88 (sum of zeros)


αβ = 125 (product of zeros)


This is only possible when both the zeroes are negative.


Question 12.

If α and β are the zeros of x2 + 5x + 8 then the value of (α + β) is
A. 5

B. ‒5

C. 8

D. ‒8


Answer:

Since, α and β are the zeroes of polynomialx2 + 5x + 8


And we know that,


x2 – (α + β) + αβ is the polynomial with α and β as its zeros


Thus, (α + β) = -5


Hence, option B is correct.


Question 13.

If α and β are the zeros of 2x2 + 5x – 9 then the value of αβ is
A.

B.

C.

D.


Answer:

Since, α and β are the zeroes of polynomial2x2 + 5x – 9


And we know that,


x2 – (α + β) + αβ is the polynomial with α and β as its zeros



Hence, option C is correct.


Question 14.

If one zero of the quadratic polynomial kx2 + 3x + k is 2 then the value of k is
A.

B.

C.

D.


Answer:

Given: 2 is the zero of the polynomial f(x) = kx2 + 3x + k


Put f(2) = 0


k(2)2 + 3(2) + k = 0


4k + 6 + k = 0



Hence, option D is correct.


Question 15.

If one zero of the quadratic polynomial (k – 1) x2 + kx + 1 is –4 then the value of k is
A.

B.

C.

D.


Answer:

Given: -4 is the zero of the polynomial f(x) = (k – 1) x2 + kx + 1


Put f(-4) = 0


(k – 1)(-4)2 + k(-4) + 1 = 0


16k -16 – 4k + 1 = 0



Hence, option B is correct.


Question 16.

If –2 and 3 are the zeros of the quadratic polynomial x2 + (a + 1) x + b then
A. a = –2, b = 6

B. a = 2, b = –6

C. a = –2, b = –6

D. a = 2, b = 6


Answer:

It is given in the question that, -2 and 3 are the zeros of x2 + (a + 1) x + b


∴ (- 2)2 + (a + 1) × (- 2) + b = 0


4 – 2a – 2 + b = 0


b – 2a = - 2 (i)


Also, we have


32 + (a + 1) × 3 + b = 0


9 + 3a + 3 + b = 0


b + 3a = - 12 (ii)


Now, by subtracting the equation (i) from (ii) we get:


a = - 2


Also, b = - 2 – 4 = - 6


Question 17.

If one zero of 3x2 + 8x + k be the reciprocal of the other then k = ?
A. 3

B. –3

C.

D.


Answer:




Thus, k = 3


Hence, option A is correct.


Question 18.

If the sum of the zeros of the quadratic polynomial kx2 + 2x + 3k is equal
A.

B.

C.

D.


Answer:

Let the zeros of the polynomial be α and β



According to the question,


α + β = αβ




Hence option D is correct.


Question 19.

If α, β are the zeros of the polynomial x2 + 6x + 2 then ?
A. 3

B. ‒3

C. 12

D. ‒12


Answer:

Given: α and βare zeros of the given polynomial.


∴α = β= -6 and αβ = 2




Hence, option B is correct.


Question 20.

If α, β, γ are the zeros of the polynomial x3 – 6x2 – x + 30 then (αβ + βγ + γ α) = ?
A. ‒1

B. 1

C. ‒5

D. 30


Answer:

Given:α, β, γ are the zeros of the polynomial x3 – 6x2 – x + 30


We know that,




Hence, option A is correct.


Question 21.

If α, β, γ are the zeros of the polynomial 2x3 + x2 – 13x + 6 then αβγ = ?
A. ‒3

B. 3

C.

D.


Answer:

Given: α, β, γ are the zeros of the polynomial 2x3 + x2 – 13x + 6

We know that,




Hence, option A is correct.


Question 22.

If α, β, γ be the zeros of the polynomial p(x) such that (α + β + γ ) = 3, (αβ + βγ + γ α) = ‒10 and αβγ = ‒24 then p(x) = ?
A. x3 + 3x210x + 24

B. x3 + 3x2 10x – 24

C. x3 – 3x2 – 10x + 24

D. None of these


Answer:

According to the question,


α, β, γ be the zeros of the polynomial p(x)such that (α + β + γ ) = 3, (αβ + βγ + γ α) = ‒10 and αβγ = ‒24


Thus, p(x) = x3 – (α + β + γ )x2 + (αβ + βγ + γ α)x - αβγ


x3 – 3x2 – 10x + 24


Hence, option C is correct.


Question 23.

If two of the zeros of the cubic polynomial az3 + bx2 + cx + d are 0 then in the third zero is
A.

B.

C.

D.


Answer:

Let5 us assume , -0 and 0 be the zeros of the given polynomial


∴ Sum of zeros =


+ 0 + 0 =


=


∴ The third zero is


Hence, option A is correct


Question 24.

If one of the zeros of the cubic polynomial ax3 + bx2 + cx + d is 0 then the product of the other two zeros is
A.

B.

C. 0

D.


Answer:

Let us assume and 0 be the zeros of the given polynomial


∴ Sum of the products of zeros taking two at a time is given by:


() =


=


The product of other two zeros will be


Hence, option B is correct


Question 25.

If one of the zeros of the cubic polynomial x3 + ax2 + bx + c is –1 then the product of the other two zeros is
A. a – b – 1

B. b – a – 1

C. 1 – a + b

D. 1 + a – b


Answer:

It is given in the question that,


- 1 is the zero of the given polynomial x3 + ax2 + bx + c


∴ (- 1)3 + a × (- 1)2 + b × (- 1) + c = 0


a – b + c + 1 = 0


c = 1 – a + b


Also, the product of all zeros is:


× (- 1) = - c


= c


= 1 – a + b


Hence, option C is correct


Question 26.

If α, β be the zeros of the polynomial 2x2 + 5x + k such that then k = ?
A. 3

B. ‒3

C. ‒2

D. 2


Answer:

It is given in the question that,


are the zeros of the given polynomial 2x2 + 5x + k


= and =


,


=


=


(-)2 =



= 1


k = 2


Hence, option D is correct


Question 27.

One dividing a polynomial p(x) by a nonzero polynomial q(x), let g(x) be the quotient and r(x) be the remainder then p(x) = q(x) g(x) + r(x), where
A. r(x) = 0 always

B. deg r(x) <deg g(x) always

C. either r(x) = 0 or deg r(x) <deg g(x)

D. r(x) = g(x)


Answer:

As, we know that


According to the division algorithm on polynomials, we have


either r (x) = 0 or deg r (x) < deg g (x)


Hence, option C is correct


Question 28.

Which of the following is a true statement?
A. x2 + 5x – 3 is a linear polynomial

B. x2 + 4x – 1 is a binomial.

C. x + 1 is a monomial.

D. 5x3 is a monomial


Answer:

We know that,


Monomial is that which consist only one term and in the given option we have only one term i.e. 5x2


∴ Option D is correct



Formative Assessment (unit Test)
Question 1.

Zeros of p(x) = x2 – 2x – 3 are
A. 1, –3

B. 3, –1

C. –3, –1

D. 1, 3


Answer:

It is given in the question that,

p (x) = x2 – 2x – 3


Let us assume x2 – 2x – 3 = 0


x2 – (3 – 1) x - 3 = 0


x2 – 3x + x – 3 = 0


x (x – 3) + 1 (x – 3) = 0


(x – 3) (x + 1) = 0


x = 3, - 1


Question 2.

If α, β, γ are the zeros of the polynomial x3 – 6x2 – x + 30 then the value of (αβ + βγ + γ α) is
A. ‒1

B. 1

C. ‒5

D. 30


Answer:

We have,

p (x) = x3 – 6x2 – x + 3


Now we will compare the given polynomial with: x3 – () x2 + () x –


By comparing we get:


() = - 1


Question 3.

If α, β are the zeros of kx2 – 2x + 3k such that α + β = αβ then k = ?
A.

B.

C.

D.


Answer:

We have,

p (x) = x2 – 2x + 3k


Now by comparing the given polynomial with ax2 + bx + c, we get:


a = 1, b = - 2 and c = 3k


In the question it is given that, are the roots of the given polynomial


=


= -( )


= 2 (i)


:


=


=


= 3k (ii)


Hence, by using (i) and (ii), we have


=


2 = 3k


k =


Question 4.

If is given that the difference between the zeros of 4x2 – 8kx + 9 is 4 and k > 0. Then k = ?
A.

B.

C.

D.


Answer:

Let us assume the zeros of the polynomial be

We have,


p (x) = 4x2 – 8kx + 9


Now comparing the given polynomial with ax2 + bx + c, we get:


a = 4, b = - 8kx + 9


Sum of roots =


=


2 + 4 = 2k


+ 2 = k


= (k – 2) (i)


, we have product of roots, =


+ 4) =


(k – 2) (k – 2 + 4) =


(k – 2) (k + 2) =


k2 – 4 =


4k2 – 16 = 9


4k2 = 25


k2 =


k =


k =


Question 5.

Find the zeros of the polynomial x2 + 2x – 195.


Answer:

We have,

p (x) = x2 + 2x – 195


Let us assume p (x) = 0


x2 + (15 – 13) x – 195 = 0


x2 + 15x – 13x – 195 = 0


x (x + 15) – 13 (x + 15) = 0


(x + 15) (x – 13) = 0


x = - 15, 13


Hence, the zeros of the polynomial are -15 and 13



Question 6.

If one zero of the polynomial (a2 + 9) x2 + 13x + 6a is the reciprocal of the other, find the value of a.


Answer:

We have,

(a + 9) x2 – 13x + 6a = 0


Comparing with standard form of quadratic equation Ax2 + Bx + C

A = (a2 + 9), B = 13 and C = 6a


Let us assume be the zeros of the given polynomial

∴ Product =


=


1 =


a2 + 9 = 6a


a2 – 6a + 9 = 0


a2 – 2 × a × 3 + 32 = 0


(a – 3)2 = 0


a – 3 = 0


a = 3


Question 7.

Find a quadratic polynomial whose zeros are 2 and ‒5.


Answer:

It is given in the question that the two roots of the given polynomial are 2 and – 5

Let us assume and = - 5


We have:


Sum of Zeros = = 2 + (-5) = - 3


Product of Zeros = = 2 × (-5) = - 10


Hence,


Required polynomial = x2 – (


= x2 – (- 3) x + 10


= x2 + 3x – 10



Question 8.

If the zeros of the polynomial x3 – 3x2 + x + 1 are (a ‒ b), a and (a + b), find the values of a and b


Answer:

It is given in the question that the roots of the given polynomial are (a – b), a and (a + b)

Now by comparing the given polynomial with Ax3 + Bx2 + Cx + D, we get:


A = 1, B = - 3, C = 1 and D = 1


Now,


(a – b) + a + (a + b) =


3a = -


a = 1


Also, we have:


(a – b) × a × (a + b) =


a (a2 – b2) =


1 (12 – b2) = - 1


1 – b2 = - 1


b2 = 2


b =


Hence, a = 1 and b =



Question 9.

Verify that 2 is a zero of the polynomial x3 + 4x2– 3x – 18.


Answer:

We have,

p (x) = x3 + 4x2 – 3x – 18


Now,


p (2) = (2)3 + 4 × (2)2 – 3 (2) – 18


= 8 + 16 – 6 – 18


= 24 – 24


= 0


∴ 2 is the zero of the given polynomial



Question 10.

Find the quadratic polynomial, the sum of whose zeros is ‒5 and their products is 6.


Answer:

It is given in the question that,

Sum of the zeros = - 5


And, product of the zeros = 6


∴ Required polynomial = x2 – (Sum of the zeros) x + Product of the zeros


= x2 – (- 5) x + 6


= x2 + 5x + 6



Question 11.

Find a cubic polynomial whose zeros are 3, 5 and ‒2.


Answer:

Let us assume be the zeros of the required polynomial

We have,


= 3 + 5 + (- 2) = 6


= 3 × 5 + 5 × (- 2) + (- 2) × 3 = - 1


And, = 3 × 5 × - 2 = - 30


Now, we have:


p (x) = x3 – x2 () + x () –


= x3 – x2 × 6 + x × (- 1) – (- 30)


= x3 – 6x2 – x + 30


Hence, the required polynomial is p (x) = x3 – 6x2 – x + 30



Question 12.

Using remainder theorem, find the remainder when p(x) = x3 + 3x2 – 5x + 4 is divided by (x ‒ 2).


Answer:

Remainder theorem:
Let p(x) be any polynomial of degree greater than or equal to one and let a be any real number. If p(x) is divided by the linear polynomial x – a, then the remainder is p(a).
It is given in the question that,

p (x) = x3 + 3x2 – 5x + 4


Now, p (2) = (2)3 + 3 (2)2 – 5 (2) + 4


= 8 + 12 – 10 + 4


= 14


Question 13.

Show that (x + 2) is a factor of f(x) = x3 + 4x2 + x – 6.


Answer:

It is given in the question that,

f (x) = x3 + 4x2 + x – 6


Now, we have


f (- 2) = (- 2)3 + 4 (- 2)2 + (- 2) - 6


= - 8 + 16 – 2 - 6


= 0


Hence, (x + 2) is a factor of f (x)



Question 14.

If α, β, γ are the zeros of the polynomial p(x) = 6x3 + 3x2 – 5x + 1, find the value of .


Answer:

It is given in the question that,

p (x) = 6x3 + 3x2 – 5x + 1


= 6x3 – (- 3) x2 + (- 5) x – 1


Now by comparing the polynomial with x3 – x2 () + x (, we get:


= - 5 and,


= - 1


()


= ()


= ()


= 5



Question 15.

If α, β are the zeros of the polynomial f(x) = x2 – 5x + k such that α ‒ β = 1, find the value of k.


Answer:

It is given in the question that,

f (x) = x2 – 5x + k such that its coefficients are a = 1, b = - 5 and c = k


=



= 5 (i)


, = 1 (ii)


, we get:


2α = 6

α = = 3


Now putting the value of α in (i), we get


3 + = 5


= 5 – 3 = 2

we know, Product of zeroes


=


Hence, k = 6


Question 16.

Show that the polynomial f(x) = x4 + 4x2 + 6 has no zero.


Answer:

Let us assume t = x2

∴ f (t) = t2 + 4t + 6


Now first of all we have to equate f (t) = 0 in order to find the zeros


∴ t =


=


= - 2


As, t = x2


So, x2 = - 2


x =


We know that, the zeros of the polynomial should be a real number and this is not a real number


∴ f (x) hs no zeros



Question 17.

If one zero of the polynomial p(x) = x3 – 6x2 + 11x – 6 is 3, find the other two zeros.


Answer:

It is given in the question that,

p (x) = x3 – 6x2 + 11x – 6 having factor (x + 3)


Now, we have to divide p (x) by (x – 3)


x3 – 6x2 + 11x – 6 = (x – 3) (x3 – 3x + 2)


= (x – 3) [(x2 – (2 + 1) x + 2]


= (x – 3) (x2 – 2x – x + 2)


= (x – 3) [x (x – 2) – 1 (x – 2)]


= (x – 3) (x - 1) (x – 2)


Hence, the two zeros of the polynomial are 1 and 2



Question 18.

If two zeros of the polynomial p(x) = 2x4 – 3x3 – 3x2 + 6x – 2 are √2 and – √2, find its other two zeros.


Answer:

It is given in the question that,

p (x) = 2x4 – 3x3 – 3x2 + 6x – 2 having zeros and -


∴ The polynomial is (x + ) (x - ) = x2 – 2


Let us now divide p (x) by (x2 – 2)


2x4 – 3x3 – 3x2 + 6x – 2 = (x2 – 2) (2x2 – 3x + 1)


= (x2 – 2) [(2x2 – (2 + 1) x + 1]


= (x2 – 2) (2x2 – 2x – x + 1)


= (x2 – 2) [(2x (x – 1) – 1 (x – 1)]


= (x2 – 2) (2x – 1) (x – 1)


Hence, the other two zeros are and 1



Question 19.

Find the quotient when p(X) = 3x4 + 5x3 – 7x2 + 2x + 2 is divided by (x2 + 3x + 1)


Answer:

It is given in the question that,

p (x) = 3x4 + 5x3 – 7x2 + 2x + 2


Now we have to divide p (x) by (x2 + 3x + 1), we get:



Hence, the quotient is 3x2 – 4x + 2



Question 20.

Use remainder theorem to find the value of k, it being given that when x3 + 2x2 + kx + 3 is divided by (x – 3), then the remainder is 21.


Answer:

Given: when x3 + 2x2 + kx + 3 is divided by (x – 3), then the remainder is 21.

To find: The value of k.

Solution:

If x-3 divides the equation and leaves 21 as remainder,
it means substituting x=3 in the equation and putting it equal to 21 will
value of k.

Let us assume,

p (x) = x3 + 2x2 + kx + 3


Now, p (3) = (3)3 + 2 (3)2 + 3k + 3


= 27 + 18 + 3k + 3


= 48 + 3k


It is given in the question that the remainder is 21


Hence, 3k + 48 = 21


3k = - 27


k = - 9