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Operations On Algebraic Expressions

Class 8th Mathematics RS Aggarwal Solution
Exercise 6a
  1. 8ab, -5ab, 3ab, -ab Add:
  2. 7x, - 3x, 5x, - x, -2x Add:
  3. 3a - 4b + 4c, 2a + 3b - 8c, a - 6b + c Add:
  4. 5x - 8y + 2z, 3z - 4y - 2x, 6y - z - x and 3x - 2x - 3y Add:
  5. 6ax - 2by + 3cz, 6by -11ax - cz and 10 cz -2ax - 3by Add:
  6. 2x^3 - 9x^2 + 8, 3x^2 - 6x - 5, 7x^3 - 10x + 1 and 3 + 2x - 5x^2 - 4x^3 Add:…
  7. 6p + 4q - r + 3, 2r - 5p - 6, 11q - 7p + 2r - 1 and 2q - 3r + 4 Add:…
  8. 4x^2 - 7xy + 4y^2 - 3, 5 + 6y^2 - 8xy + x^2 and 6 - 2xy + 2x^2 - 5y^2 Add:…
  9. 2a^2 b from - 5a^2 b Subtract:
  10. -8pq from 6pq Subtract:
  11. -2abc from -8abc Subtract:
  12. -16p from -11 p Subtract:
  13. 2a - 5b + 2c - 9 from 3a - 4b - c + 6 Subtract:
  14. -6p + q + 3r + 8 from p - 2q - 5r - 8 Subtract:
  15. x^3 + 3x^2 - 5x + 4 from 3x^3 - x^2 + 2x - 4 Subtract:
  16. 5y^4 - 3y^3 + 2y^2 + y - 1 from 4y^4 - 2y^3 - 6y^2 - y + 5 Subtract:…
  17. 4p^2 + 5q^2 - 6r^2 + 7 from 3p^2 - 4q^2 - 5r^2 - 6 Subtract:
  18. What must be subtracted from 3a^2 - 6ab - 3b^2 - 1 to get 4a^2 - 7ab - 4ab^2 +…
  19. The two adjacent sides of a rectangle are 5x^2 - 3y^2 and x^2 + 2xy. Find the…
  20. The perimeter of triangle is 6p^2 - 4p + 9 and two of its sides are p^2 - 2p +…
Exercise 6b
  1. (5x + 7) (3x + 4) Find each of the following products:
  2. (4x + 9) (x - 6) Find each of the following products:
  3. (2x + 5) (4x - 3) Find each of the following products:
  4. (3y - 8) (5y - 1) Find each of the following products:
  5. (7x + 2y) (x + 4y) Find each of the following products:
  6. (9x + 5y) (4x + 3y) Find each of the following products:
  7. (3m - 4n) (2m - 3n) Find each of the following products:
  8. (x^2 - a^2) (x - a) Find each of the following products:
  9. (x^2 - y^2) (x + 2y) Find each of the following products:
  10. (3p^2 + q^2) (2p^2 - 3q^2) Find each of the following products:
  11. (2x^2 - 5y^2) (x^2 + 3y^2) Find each of the following products:
  12. (x^3 - y^3) (x^2 + y^2) Find each of the following products:
  13. (x^4 + y^4) (x^2 - y^2) Find each of the following products:
  14. (x^4 + 1/x^4) x (x + 1/x) Find each of the following products:
  15. (x^2 - 3x + 7) (2x + 3) Find each of the following products:
  16. (3x^2 + 5x - 9) (3x - 5) Find each of the following products:
  17. (x^2 - xy + y^2) (x + y) Find each of the following products:
  18. (x^2 + xy + y^2) (x - y) Find each of the following products:
  19. (x^3 - 2x^2 + 5) (4x - 1) Find each of the following products:
  20. (9x^2 - x + 15) (x^2 - 3) Find each of the following products:
  21. (x^2 - 5x + 8) (x^2 + 2) Find each of the following products:
  22. (x^3 - 5x^2 + 3x + 1) (x^2 - 3) Find each of the following products:…
  23. (3x + 2y - 4) (x - y + 2) Find each of the following products:
  24. (x^2 - 5x + 8) (x^2 + 2x - 3) Find each of the following products:…
  25. (2x^2 + 3x - 7) (3x^2 - 5x + 4) Find each of the following products:…
  26. Find each of the following products: (9x^2 - x + 15) (x^2 - x - 1)…
Exercise 6c
  1. (i) 24x^2 y^3 by 3xy (ii) 36xyz^2 by - 9xz (iii) - 72x^2 y^2 z by- 12xyz (iv) -…
  2. (i) 5m^3 - 30m^2 + 45m by 5m (ii) 8x^2 y^2 - 6xy^2 + 10x^2 y^3 by 2xy (iii) 9x^2…
  3. (x^2 - 4x + 4) by (x - 2) Write the quotient and remainder when we divide:…
  4. (x^2 - 4) by (x + 2) Write the quotient and remainder when we divide:…
  5. (x^2 + 12x + 35) by (x + 7) Write the quotient and remainder when we divide:…
  6. (15x^2 + x - 6) by (3x + 2) Write the quotient and remainder when we divide:…
  7. (14x^2 - 53x + 45) by (7x - 9) Write the quotient and remainder when we divide:…
  8. (6x^2 - 31x + 47) by (2x - 5) Write the quotient and remainder when we divide:…
  9. (2x^3 + x^2 - 5x - 2) by (2x + 3) Write the quotient and remainder when we…
  10. (x^3 + 1) by (x + 1) Write the quotient and remainder when we divide:…
  11. (x^4 - 2x^3 + 2x^2 + x + 4) by (x^2 + x + 1) Write the quotient and remainder…
  12. (x^3 - 6x^2 + 11x - 6) by (x^2 - 5x + 6) Write the quotient and remainder when…
  13. (5x^3 - 12x^2 + 12x + 13) by (x^2 - 3x + 4) Write the quotient and remainder…
  14. (2x^3 - 5x^2 + 8x - 5) by (2x^2 - 3x + 5) Write the quotient and remainder when…
  15. (8x^4 + 10x^3 - 5x^2 - 4x + 1) by (2x^2 - 3x + 5) Write the quotient and…
Exercise 6d
  1. (i) (x + 6)(x+6) (ii) (4x + 5y)(4x + 5y) (iii) (7a + 9b)(7a + 9b) (iv) (2/3 x +…
  2. (i) (x - 4)(x - 4) (ii) (2x - 3y)(2x - 3y) (iii) (3/4 x - 5/6 y) (3/4 x - 5/6 y)…
  3. Expand: (i) (8a + 3b)^2 (ii) (7x + 2y)^2 (iii) (5x + 11)^2 (iv) (a/2 + 2/a)^2…
  4. (i) (x + 3)(x - 3) (ii) (2x + 5)(2x - 5) (iii) (8 + x)(8 - x) (iv) (7x + 11y)(7x…
  5. (i) (54)^2 (ii) (82)^2 (iii) (103)^2 (iv) (704)^2 Using the formula for squaring…
  6. (i) (69)^2 (ii) (78)^2 (iii) (197)^2 (iv) (999)^2 Using the formula for squaring…
  7. Find the value of: (i) (82)^2 - (18)^2 (ii) (128)^2 - (72)^2 (iii) 197 203 (iv)…
  8. Find the value of the expression (9x^2 + 24x + 16), when x = 12.
  9. Find the value of the expression (64x^2 + 81y^2 + 144xy), when x = 11 and y =…
  10. Find the value of the expression (36x^2 + 25y^2 - 60xy) when x = 2/3 and y =…
  11. If (x + 1/x) = 4 find the values of (i) (x^2 + 1/x^2) (ii) (x^4 + 1/x^4)…
  12. If (x - 1/x) = 5 find the value of (i) (x^2 + 1/x^2) (ii) (x^4 + 1/x^4)…
  13. Find the continued product: (i) (x +1)(x - 1)(x^2 + 1) (ii) (x- 3)(x + 3)(x^2 +…
  14. If x + y = 12 and xy = 14, find the value of (x^2 + y^2).
  15. If x - y = 7 and xy = 9, find the value of (x^2 + y^2).
Exercise 6e
  1. The sum of (6a + 4b - c + 3), (2b - 3c + 4), (11b - 7a + 2c - 1) and (2c - 5a -…
  2. (3q + 7p^2 - 2r^3 + 4) - (4p^2 - 2q + 7r^3 - 3) = ?A. (p^2 + 2q+5r^2 + 1) B.…
  3. (x + 5) (x - 3) = ?A. x^2 + 5x-15 B. x^2 - 3x-15 C. x^2 + 2x+15 D. x^2 + 2x-15…
  4. (2x + 3)(3x - 1) = ?A. (6x^2 + 8x-3) B. (6x^2 + 7x-3) C. 6x^2 - 7x-3 D. (6x^2 -…
  5. (x + 4)(x + 4) = ?A. (x^2 + 16) B. (x^2 + 4x+16) C. (x^2 + 8x+16) D. (x^2 + 16x)…
  6. (x - 6)(x - 6) = ?A. (x^2 - 36) B. (x^2 + 36) C. (x^2 - 6x+36) D. (x^2 - 12x+36)…
  7. (2x + 5)(2x - 5) = ?A. (4x^2 + 25) B. (4x^2 - 25) C. (4x^2 - 10x+25) D. (4x^2 +…
  8. 8a^2 b^3 (- 2ab) = ?A. 4ab^2 B. 4a^2b C. -4ab^2 D. -4a^2b
  9. (2x^2 + 3x + 1) (x + 1) = ?A. (x+1) B. (2x+1) C. (x+3) D. (2x+3)
  10. (x^2 - 4x + 4) (x - 2) = ?A. (x-2) B. (x+2) C. (2-x) D. (2+x+x^2)…
  11. (a + 1)(a - 1)(a^2 + 1) = ?A. (a^4 - 2a^2 - 1) B. (a^4 - a^2 - 1) C. (a^4 - 1)…
  12. (1/x + 1/y) (1/x - 1/y) = ? A. (1/x^2 - 1/y^2) B. (1/x^2 + 1/y^2) C. (1/x^2 +…
  13. If (x + 1/x) = 5 then (x^2 + 1/x^2) = ? A. 25 B. 27 C. 23 B. 25 1/25…
  14. If (x - 1/x) = 6 then (x^2 + 1/x^2) = ? A. 36 B. 38 C. 32 D. 36 1/36…
  15. (82)^2 - (18)^2 = ?A. 8218 B. 6418 C. 6400 D. 7204
  16. (197 203) = ?A. 39991 B. 39999 C. 40009 D. 40001
  17. If (a + b) = 12 and ab = 14, then (a^2 + b^2) = ?A.172 B. 116 C. 162 D. 126…
  18. If (a - b) = 7 and ab = 9, then (a^2 + b^2) = ?A. 67 B. 31 C. 40 D. 58…
  19. If x = 10, then find the value of (4x^2 + 20x + 25).A. 256 B. 425 C. 625 D. 575…

Exercise 6a
Question 1.

Add:

8ab, -5ab, 3ab, -ab


Answer:

To add the expressions, we have to arrange the given expression in the form of rows and then add the expression column wise, so we have;




Question 2.

Add:

7x, - 3x, 5x, – x, -2x


Answer:

To add the expressions, we have to arrange the given expression in the form of rows and then add the expression column wise, so we have;




Question 3.

Add:

3a – 4b + 4c, 2a + 3b – 8c, a – 6b + c


Answer:

To add the expressions, we have to arrange the given expression in the form of rows and then add the expression column wise, so we have;




Question 4.

Add:

5x – 8y + 2z, 3z – 4y – 2x, 6y – z – x and 3x – 2x – 3y


Answer:

To add the expressions, we have to arrange the given expression in the form of rows and then add the expression column wise, so we have;




Question 5.

Add:

6ax – 2by + 3cz, 6by -11ax – cz and 10 cz -2ax – 3by


Answer:

To add the expressions, we have to arrange the given expression in the form of rows and then add the expression column wise, so we have;




Question 6.

Add:

2x3 – 9x2 + 8, 3x2 – 6x – 5, 7x3 – 10x + 1 and 3 + 2x – 5x2 – 4x3


Answer:

Let’s arrange the data in a table in the form of descending power of x,


We will get rows and columns; add the data column wise;



So, the answer after adding all the expressions will be;


5x3 - 11x2 – 14x + 7



Question 7.

Add:

6p + 4q – r + 3, 2r - 5p – 6, 11q - 7p + 2r – 1 and 2q – 3r + 4


Answer:

To add the expressions, we have to arrange the given expression in the form of rows and then add the expression column wise, so we have;



So, the answer is;


– 6p + 17q



Question 8.

Add:

4x2 – 7xy + 4y2 – 3, 5 + 6y2 – 8xy + x2 and 6 – 2xy + 2x2 – 5y2


Answer:

By arrange the given expression in descending powers of x it will be easier To add the expressions,s,


So, we have;




Question 9.

Subtract:

2a2b from – 5a2b


Answer:

We have to subtract 3a2b from – 5a2b.


According to the rule when both the expressions have negative sign so we add both the expression and put negative sign only.


So, by arranging the data in rows and columns form we have;




Question 10.

Subtract:

–8pq from 6pq


Answer:

According to the rule of subtraction two negative becomes positive and the result will have negative sign.


So, To subtract the expression,we have to arrange the given expression in the form of rows and then subtract the expression column wise,


Therefore, we have;




Question 11.

Subtract:

–2abc from –8abc


Answer:

According to the rule of subtraction two negative becomes positive and the result will have negative sign.


To subtract the expression, we have to arrange the given expression in the form of rows and then subtract the expression column wise, so we have;




Question 12.

Subtract:

–16p from –11 p


Answer:

According to the rule of subtraction two negative becomes positive and the result will have negative sign.


To subtract the expression,we have to arrange the given expression in the form of rows and then subtract the expression column wise, so we have;




Question 13.

Subtract:

2a – 5b + 2c – 9 from 3a – 4b – c + 6


Answer:

According to the rule of subtraction two negative becomes positive and the result will have negative sign.


To subtract the expression,we have to arrange the given expression in the form of rows and then subtract the expression column wise, so we have;




Question 14.

Subtract:

–6p + q + 3r + 8 from p – 2q – 5r – 8


Answer:

According to the rule of subtraction two negative becomes positive and the result will have negative sign.


To subtract the expression,we have to arrange the given expression in the form of rows and then subtract the expression column wise, so we have;




Question 15.

Subtract:

x3 + 3x2 – 5x + 4 from 3x3 – x2 + 2x – 4


Answer:

According to the rule of subtraction two negative becomes positive and the result will have negative sign.


To subtract the expression,we have to arrange the given expression in the form of rows and then subtract the expression column wise, so we have;




Question 16.

Subtract:

5y4 – 3y3 + 2y2 + y – 1 from 4y4 – 2y3 – 6y2 – y + 5


Answer:

According to the rule of subtraction two negative becomes positive and the result will have negative sign.


To subtract the expression,we have to arrange the given expression in the form of rows and then subtract the expression column wise, so we have;




Question 17.

Subtract:

4p2 + 5q2 – 6r2 + 7 from 3p2 – 4q2 – 5r2 – 6


Answer:

According to the rule of subtraction two negative becomes positive and the result will have negative sign.


To subtract the expression,we have to arrange the given expression in the form of rows and then subtract the expression column wise, so we have;




Question 18.

What must be subtracted from 3a2 – 6ab – 3b2 – 1 to get 4a2 – 7ab – 4ab2 + 1?


Answer:

Let’s suppose the required number be x,


So we have;


(3a2 – 6ab – 3b2 – 1) – x = 4a2 – 7a – 4b2 + 1


(3a2 – 6ab – 3b2 – 1) – (4a2 – 7a – 4b2 + 1) = x


So,


To get the required number we have to subtract 4a2 – 7a – 4b2 + 1 from 3a2 – 6ab – 3b2 - 1



So, the required number is - a2 + ab + b2 – 2



Question 19.

The two adjacent sides of a rectangle are 5x2 – 3y2 and x2 + 2xy. Find the perimeter.


Answer:

We know that;


Two adjacent sides of a rectangle are l and b;


l = 5x2 – 3y2


b = x2 + 2xy


Perimeter of rectangle = (2l+2b)


Which is;


2 (5x2 – 3y2) + 2(x2 + 2xy)


= (10x2 – 6y2) + (2x2 + 4xy)




Question 20.

The perimeter of triangle is 6p2 – 4p + 9 and two of its sides are p2 – 2p + 1 and 3p2 – 5p + 3. Find the third side of the triangle.


Answer:

Perimeter of the triangle = 6p2 – 4p + 9


Two sides are;


Side one = p2 – 2p + 1 and


Side two = 3p2 – 5p + 3


Let’s take third side be = x


As we know perimeter of a triangle = sum of all the sides


So, we have


6p2 – 4p + 9 = {(p2 – 2p + 1) + (3p2 – 5p + 3) + (x)}


6p2 – 4p + 9 = p2 – 2p + 1 + 3p2 – 5p + 3 + x


6p2 – 4p + 9 - p2 + 2p – 1 - 3p2 + 5p - 3 = x


Let’s make the pairs;


(6p2 – p2 – 3p2) + (- 4p + 2p + 5p) + (9 – 1 – 3) = x


2p2 + 3p + 5 = x


The required side is 2p2 + 3p + 5.








Exercise 6b
Question 1.

Find each of the following products:

(5x + 7) × (3x + 4)


Answer:

To find the product of the given expression we have to Horizontal method;


Horizontal method is the method where each term of one expression is multiplied with each term of other expression.


So, by using horizontal method,


We have;


= (5x + 7) × (3x + 4)


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


= 15x2 + 20x + 21x + 28


= 15x2 41x + 28



Question 2.

Find each of the following products:

(4x + 9) × (x – 6)


Answer:

By using horizontal method,


We have;


= (4x + 9) × (x - 6)


= 4x(x – 6) + 9(x - 6)


= 4x2 – 24x + 9x – 54


= 4x2 – 15x – 54



Question 3.

Find each of the following products:

(2x + 5) × (4x – 3)


Answer:

By using horizontal method,


We have;


= (2x + 5) × (4x - 3)


= 2x (4x – 3) + 5 (4x – 3)


= 8x2 - 6x + 20x – 15


= 8x2 + 14x - 15



Question 4.

Find each of the following products:

(3y – 8) × (5y – 1)


Answer:

By using horizontal method,


We have;


= (3y - 8) × (5y - 1)


= 3y(5y – 1) – 8(5y – 1)


= 15y2 – 3y – 40y + 8


= 15y2 – 43y +8



Question 5.

Find each of the following products:

(7x + 2y) × (x + 4y)


Answer:

By using horizontal method,


We have;


= (7x + 2y) × (x + 4y)


= 7x(x +4y) + 2y(x + 4y)


= 7x2 + 28xy + 2xy + 8y2


= 7x2 + 30xy + 8y2



Question 6.

Find each of the following products:

(9x + 5y) × (4x + 3y)


Answer:

By using horizontal method,


We have;


= (9x + 5y) × (4x + 3y)


= 9x(4x + 3y) + 5y(4x + 3y)


= 36x2 + 27xy + 20xy + 15y2


= 36x2 + 47xy + 15y2



Question 7.

Find each of the following products:

(3m – 4n) × (2m – 3n)


Answer:

By using horizontal method,


We have;


= (3m – 4n) × (2m – 3n)


= 3m(2m – 3n) – 4n(2m – 3n)


= 6m2 – 9mn – 8mn + 12n2


= 6m2 – 17mn + 12n2



Question 8.

Find each of the following products:

(x2 – a2) × (x – a)


Answer:

By using horizontal method,


We have;


= (x2 – a2) × (x – a)


= x2(x – a) – a2(x – a)


= x3 – ax2 – a2x + a3



Question 9.

Find each of the following products:

(x2 – y2) × (x + 2y)


Answer:

By using horizontal method,


We have;


= (x2 – y2) × (x + 2y)


= x2 (x + 2y) – y2(x + 2y)


= x3 + 2x2y – xy2 – 2y3



Question 10.

Find each of the following products:

(3p2 + q2) × (2p2 – 3q2)


Answer:

By using horizontal method,


We have;


= (3p2 + q2) × (2p2 – 3q2)


= 3p2(2p2 – 3q2) + q2(2p2 – 3q2)


= 6p4 – 9p2q2 + 2p2q2 – 3q4


= 6p4 – 7p2q2 – 3q4



Question 11.

Find each of the following products:

(2x2 – 5y2) × (x2 + 3y2)


Answer:

By using horizontal method,


We have;


= (2x2 – 5y2) × (x2 + 3y2)


= 2x2(x2 + 3y2) – 5y2(x2 + 3y2)


= 2x4 + 6x2y2 – 5x2y2 – 15y4


= 2x4 + x2y2 – 15y4



Question 12.

Find each of the following products:

(x3 – y3) × (x2 + y2)


Answer:

By using horizontal method,


We have;


= (x3 – y3) × (x2 + y2)


= x3(x2 + y2) – y3(x2 + y2)


= x5 + x3y2 – x2y3 - y5



Question 13.

Find each of the following products:

(x4 + y4) × (x2 – y2)


Answer:

By using horizontal method,


We have;


= (x4 + y4) × (x2 – y2)


= x4(x2 – y2) + y4(x2 – y2)


= x6 – x4y2 + x2y4 – y6



Question 14.

Find each of the following products:



Answer:

By using horizontal method,


We have;






Question 15.

Find each of the following products:

(x2 – 3x + 7) × (2x + 3)


Answer:

By using horizontal method,


We have;


= (x2 – 3x + 7) × (2x + 3)


= 2x(x2 – 3x + 7) + 3(x2 – 3x + 7)


= 2x3 - 6x2 + 14x + 3x2 – 9x + 21


By arranging the expression in the form of descending powers of x,


We get;


= 2x3 – 6x2 + 3x2 + 14x – 9x + 21


= 2x3 – 3x2 + 5x + 21



Question 16.

Find each of the following products:

(3x2 + 5x - 9) × (3x – 5)


Answer:

By using horizontal method,


We have;


= (3x2 + 5x – 9) × (3x – 5)


= 3x(3x2 + 5x – 9) – 5(3x2 + 5x – 9)


= 9x3 + 15x2 – 27x – 15x2 - 25x + 45


By arranging the expression in the form of descending powers of x,


We get;


= 9x3 + 15x2 – 15x2 – 27x – 25x + 45


= 9x3 – 52x + 45



Question 17.

Find each of the following products:

(x2 – xy + y2) × (x + y)


Answer:

By using horizontal method,


We have;


= (x2 – xy + y2) × (x + y)


= x(x2 – xy + y2) + y(x2 – xy + y2)


= x3 - x2y + xy2 + x2y – xy2 + y3


By arranging the expression in the form of descending powers of x,


We get;


= (x3 + y3)



Question 18.

Find each of the following products:

(x2 + xy + y2) × (x – y)


Answer:

By using horizontal method,


We have;


= (x2 + xy + y2) × (x - y)


= x(x2 + xy + y2) - y(x2 + xy + y2)


= x3 + x2y + xy2 - x2y – xy2 - y3


By arranging the expression in the form of descending powers of x,


We get;


= (x3 - y3)



Question 19.

Find each of the following products:

(x3 – 2x2 + 5) × (4x - 1)


Answer:

By using horizontal method,


We have;


= (x3 – 2x2 + 5) × (4x – 1)


= 4x(x3 – 2x2 + 5) – 1(x3 – 2x2 + 5)


= 4x4 – 8x3 + 20x – 1x3 + 2x2 – 5


By arranging the expression in the form of descending powers of x,


We get;


= 4x4 – 8x3 – x3 + 2x2 + 20x – 5


= 4x4 – 9x3 + 2x2 + 20x – 5



Question 20.

Find each of the following products:

(9x2 – x + 15) × (x2 – 3)


Answer:

By using horizontal method,


We have;


= (9x2 – x + 15) × (x2 – 3)


= x2(9x2 – x +15) – 3(9x2 – x + 15)


= 9x4 – x3 + 15x2 – 27x2 + 3x – 45


= 9x4 - x3 – 12x2 + 3x – 45



Question 21.

Find each of the following products:

(x2 – 5x + 8) × (x2 + 2)


Answer:

By using horizontal method,


We have;


= (x2 – 5x + 8) × (x2 + 2)


= x2(x2 – 5x + 8) + 2(x2 – 5x + 8)


= x4 – 5x3 + 8x2 + 2x2 – 10x + 16


= x4 – 5x3 + 10x2 – 10x +16



Question 22.

Find each of the following products:

(x3 – 5x2 + 3x + 1) × (x2 – 3)


Answer:

By using horizontal method,


We have;


= (x3 – 5x2 + 3x + 1) × (x2 – 3)


= x2(x3 – 5x2 + 3x + 1) – 3(x3 – 5x2 + 3x +1)


= x5 – 5x4 + 3x3 + x2 – 3x3 + 15x2 – 9x – 3


By arranging the expression in the form of descending powers of x,


We get;


= x5 – 5x4 + 3x3 – 3x3 + x2 + 15x2 – 9x – 3


= x5 – 5x4 +16x2 – 9x – 3



Question 23.

Find each of the following products:

(3x + 2y – 4) × (x – y + 2)


Answer:

By using horizontal method,


We have;


= (3x + 2y – 4) × (x – y + 2)


= x(3x + 2y – 4) – y(3x + 2y – 4) + 2(3x + 2y – 4)


= 3x2 + 2xy – 4x – 3xy – 2y2 + 4y + 6x + 4y – 8


By arranging the expression in the form of descending powers of x,


We get;


= 3x2 – 4x + 6x + 2xy – 3xy – 2y2 + 4y + 4y – 8


= 3x2 + 2x – xy – 2y2 + 8y – 8



Question 24.

Find each of the following products:

(x2 – 5x + 8) × (x2 + 2x – 3)


Answer:

By using horizontal method,


We have;


= (x2 – 5x + 8) × (x2 + 2x – 3)


= x2(x2 – 5x + 8) + 2x(x2 – 5x + 8) – 3(x2 – 5x + 8)


= x4 – 5x3 + 8x2 + 2x3 – 10x2 + 16x – 3x2 + 15x – 24


By arranging the expression in the form of descending powers of x,


We get;


= x4 – 3x3 – 5x2 + 31x – 24



Question 25.

Find each of the following products:

(2x2 + 3x – 7) × (3x2 – 5x + 4)


Answer:

By using horizontal method,


We have;


(2x2+ 3x – 7) ×(3x2 – 5x + 4)


= 2x2(3x2 – 5x + 4) + 3x(3x2 – 5x + 4) – 7(3x2 – 5x + 4)


= 6x4 – 10x3 + 8x2 + 9x3 – 15x2 + 12x– 21x2 + 35x – 28


Now, putting equal power terms together, we get,


= 6x4 – 10x3 + 9x3 + 8x2 – 15x2– 21x2 + 35x + 12x– 28


= 6x4 – x3 – 28x2 + 47x – 28



Question 26.

Find each of the following products:

(9x2 – x + 15) × (x2 – x – 1)






Answer:

By using horizontal method,


We have;


(9x2 – x + 15) × (x2 – x – 1)


= 9x2(x2 – x – 1) – x (x2 – x – 1) +15(x2 – x – 1)


= 9x4 – 9x3 – 9x2 – x3 + x2 + x + 15x2 – 15x – 15


Putting equal power terms together, we get,


= 9x4 – 9x3 – x3 – 9x2 + x2 + 15x2 – 15x + x – 15


= 9x4 – 10x3 + 7x2 – 14x – 15




Exercise 6c
Question 1.

Divide:

(i) 24x2y3 by 3xy

(ii) 36xyz2 by – 9xz

(iii) – 72x2y2z by– 12xyz

(iv) – 56mnp2 by 7mnp


Answer:

(i) By dividing 24x2y3 by 3xy


We get;



= 8xy2


(ii) By dividing 36xyz2 by by – 9xz


We get;



= - 4yz


(iii) By dividing – 72x2y2z by – 12xyz


We get;



= 6xy


(iv) By dividing – 56mnp2 by 7mnp


We get;



= - 8p



Question 2.

Divide:

(i) 5m3 – 30m2 + 45m by 5m

(ii) 8x2y2 – 6xy2 + 10x2y3 by 2xy

(iii) 9x2y – 6xy + 12xy2 by – 3xy

(iv) 12x4 + 8x3 – 6x2 by – 2x2


Answer:

(i) By dividing 5m3 – 30m2 + 45m by 5m


We get;




= m2 – 6m + 9


(ii) By dividing 8x2y2 – 6xy2 + 10x2y3 by 2xy


We get;




= 4xy – 3y + 5xy2


(iii) If we divide 9x2y – 6xy + 12xy2 by – 3xy


We get;




= - 3x + 2 – 4y


(iv) If we divide 12x4 + 8x3 – 6x2 by – 2x2


We get;




= - 6x2 – 4x + 3



Question 3.

Write the quotient and remainder when we divide:

(x2 – 4x + 4) by (x – 2 )


Answer:

If we divide x2 – 4x + 4 by x -2;



So, we get;


Quotient = x – 2 and remainder = 0



Question 4.

Write the quotient and remainder when we divide:

(x2 – 4) by (x + 2)


Answer:

If we divide (x2 – 4) by (x + 2);



So, we get;


Quotient = x – 2 and remainder = 0



Question 5.

Write the quotient and remainder when we divide:

(x2 + 12x + 35) by (x + 7)


Answer:

If we divide (x2 + 12x + 35) by (x + 7)



So, we get;


Quotient = (x + 5) and remainder = 0



Question 6.

Write the quotient and remainder when we divide:

(15x2 + x – 6) by (3x + 2)


Answer:

If we divide (15x2 + x – 6) by (3x + 2)



We get;


Quotient = (5x – 3) and remainder = 0



Question 7.

Write the quotient and remainder when we divide:

(14x2 – 53x + 45) by (7x – 9)


Answer:

If we divide (14x2 – 53x + 45) by (7x – 9)


So we get;



Quotient = 2x - 5 and remainder = 0



Question 8.

Write the quotient and remainder when we divide:

(6x2 – 31x + 47) by (2x – 5)


Answer:

By dividing the given expressions we get;



Quotient = (3x – 8) and remainder = 7



Question 9.

Write the quotient and remainder when we divide:

(2x3 + x2 – 5x – 2) by (2x + 3)


Answer:

By dividing the given expressions we get;



Quotient = (x2 – x – 1) and remainder = 1



Question 10.

Write the quotient and remainder when we divide:

(x3 + 1) by (x + 1)


Answer:

By dividing the given expressions we get;



Quotient = (x2 – x + 1) and remainder = 0



Question 11.

Write the quotient and remainder when we divide:

(x4 – 2x3 + 2x2 + x + 4) by (x2 + x + 1)


Answer:

By dividing the given expressions we get;



Quotient = x2 – 3x + 4 and remainder = 0



Question 12.

Write the quotient and remainder when we divide:

(x3 – 6x2 + 11x – 6) by (x2 – 5x + 6)


Answer:

By dividing the given expressions we get;



Quotient = (x – 1) and remainder = 0



Question 13.

Write the quotient and remainder when we divide:

(5x3 – 12x2 + 12x + 13) by (x2 – 3x + 4)


Answer:

By dividing the given expressions we get;



Quotient = (5x + 3) and remainder = (x + 1)



Question 14.

Write the quotient and remainder when we divide:

(2x3 – 5x2 + 8x – 5) by (2x2 – 3x + 5)


Answer:

By dividing the given expressions we get;



Quotient = (x – 1) and remainder = 0



Question 15.

Write the quotient and remainder when we divide:

(8x4 + 10x3 – 5x2 – 4x + 1) by (2x2 – 3x + 5)


Answer:

If we divide (8x4 + 10x3 – 5x2 – 4x + 1) by (2x2 – 3x + 5)


We get,



So,


We get the quotient 4x2 + 11x + 4


And the remainder – 47x – 19




Exercise 6d
Question 1.

Find each of the following products:

(i) (x + 6)(x+6)

(ii) (4x + 5y)(4x + 5y)

(iii) (7a + 9b)(7a + 9b)

(iv)

(v) (x2 + 7)(x2 + 7)

(vi)


Answer:

(i) As we have (x + 6)(x+6)


(x + 6)(x + 6) = (x + 6)2


By using the formula;


[(a + b)2 = a2 + b2 + 2ab]


We get,


(x + 6)2 = x2 + (6)2 + 2× (x) × (6)


= x2 + 36 + 12x


By arranging the expression in the form of descending powers of x we get;


= x2 + 12x + 36


(ii) Given;


(4x + 5y)(4x + 5y)


By using the formula;


[(a + b)2 = a2 + b2 + 2ab]


We get,


(4x + 5y)(4x + 5y) = (4x + 5y)2


(4x + 5y)2 = (4x)2 + (5y)2 + 2 × (4x) ×(5y)


= 16x2 + 25y2 + 40xy


(iii) Given,


(7a + 9b)(7a + 9b)


By using the formula;


[(a + b)2 = a2 + b2 + 2ab]


We get,


(7a + 9b)(7a + 9b) = (7a + 9b)2


(7a + 9b)2 = (7a)2 + (9b)2 + 2 × (7a) × (9b)


= 49a2 + 81b2 + 126ab


(iv)


By using the formula (a + b)2


We get;





(v) (x2 + 7)(x2 + 7)


By using the formula (a + b)2


We get;


(x2 + 7)(x2 + 7) = (x2 + 7)2


= (x2)2 +(7)2 + 2 × (x2) × (7)


= x4 + 49 + 14x2


(vi)


By using the formula (a + b)2


We get;







Question 2.

Find each of the following products:

(i) (x – 4)(x – 4)

(ii) (2x – 3y)(2x – 3y)

(iii)

(iv)

(v)

(vi)


Answer:

(i) Given,


(x – 4)(x – 4)


By using the formula (a – b)2 = a2 – 2ab + b2


We get;


= (x – 4)2


= (x)2 – 2 × (x) × 4 + (4)2


= x2 – 8x + 16


(ii) Given,


(2x – 3y)(2x – 3y)


By using the formula (a – b)2 = a2 – 2ab + b2


We get;


= (2x – 3y)2


= (2x)2 – 2 × (2x) × (3y) + (3y)2


= 4x2 – 12xy + 9y2


(iii)


By using the formula (a – b)2 = a2 – 2ab + b2


We get;






(iv)


By using the formula (a – b)2 = a2 – 2ab + b2


We get;






(v)


By using the formula (a – b)2 = a2 – 2ab + b2


We get;





(vi)


By using the formula (a – b)2 = a2 – 2ab + b2


We get;







Question 3.

Expand:

(i) (8a + 3b)2 (ii) (7x + 2y)2

(iii) (5x + 11)2 (iv)

(v) (vi) (9x – 10)2

(vii) (viii)

(ix)


Answer:

(i) Given,


(8a + 3b)2


By using the formula (a + b)2 = a2 + b2 + 2ab


We get;


= (8a)2 + (3b)2 + 2 × 8a × 3b


= 64a2 + 9b2 + 48ab


(ii) (7x + 2y)2


By using the formula (a + b)2 = a2 + b2 + 2ab


We get;


= (7x)2 + (2y)2 + 2 × (7x) × (2y)


= 49x2 + 4y2 + 28xy


(iii) (5x + 11)2


By using the formula (a + b)2 = a2 + b2 + 2ab


We get;


= (5x)2 + (11)2 + 2×(5x) × 11


= 25x2 + 121 + 110x


(iv)


By using the formula (a + b)2 = a2 + b2 + 2ab


We get;





(v)


By using the formula (a + b)2 = a2 + b2 + 2ab


We get;




(vi) (9x – 10)2


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


We get;


(9x – 10)2


= (9x)2 – 2 × (9x) × 10 + (10)2


= 81x2 – 180x + 100


(vii) (x2y – yz2)2


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


We get;


= (x2y – yz2)2


= (x2y)2 – 2 × (x2y) × yz2 + (yz2)2


= x4y2 – 2x2y2z2 + y2z4


(viii)


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


We get;



(ix)


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


We get;


=




Question 4.

Find each of the following products:

(i) (x + 3)(x – 3)

(ii) (2x + 5)(2x – 5)

(iii) (8 + x)(8 – x)

(iv) (7x + 11y)(7x – 11y)

(v)

(vi)

(vii)

(viii)

(ix)


Answer:

(i) Given,


(x + 3)(x – 3)


By using the formula (a + b) (a – b) = a2 – b2


We get;


= x(x + 3) – 3(x + 3)


= x2 + 3x – 3x – 9


= x2 – 9


(ii) Given,


(2x + 5)(2x – 5)


By using the formula (a + b) (a – b) = a2 – b2


We get;


= 2x(2x + 5) – 5(2x + 5)


= 4x2 + 10x – 10x – 25


= 4x2 – 25


(iii) Given,


(8 + x)(8 – x)


By using the formula (a + b) (a – b) = a2 – b2


We get;


= 8(8 + x) – x(8 + x)


= 64 + 8x – 8x – x2


= 64 – x2


(iv) Given,


(7x + 11y)(7x – 11y)


By using the formula (a + b) (a – b) = a2 – b2


We get;


= 7x(7x + 11y) – 11y(7x + 11y)


= 49x2 + 77xy – 77xy – 121y2


= 49x2 – 121y2


(v) Given,



By using the formula (a + b) (a – b) = a2 – b2


We get;




(vi)


By using the formula (a + b) (a – b) = a2 – b2


We get;



(vii)


By using the formula (a + b) (a – b) = a2 – b2


We get;



(viii)


By using the formula (a + b) (a – b) = a2 – b2


We get;



(ix)


By using the formula (a + b) (a – b) = a2 – b2


We get;




Question 5.

Using the formula for squaring a binomial, evaluate the following:

(i) (54)2 (ii) (82)2

(iii) (103)2 (iv) (704)2


Answer:

(i) Given,


(54)2


If we break the given number we get;


(50 + 4)2


Now we can use the (a + b)2 = a2 + b2 + 2ab


So,


= (50 + 4)2 = (50)2 + (4)2 + 2 × 50 × 4


= 2500 + 16 + 400


= 2916


(ii) (82)2


We can also write it as;


(80 + 2)2


By using the formula (a + b)2 = a2 + b2 + 2ab


We get,


= (80 + 2)2 = (80)2 + (2)2 + 2 × 80 × 2


= 6400 + 4 + 320


= 6724


(iii) (103)2


We can also write it as;


(100 + 3)2


By using the formula (a + b)2 = a2 + b2 + 2ab


We get,


(100 + 3)2 = (100)2 + (3)2 + 2 × 100 × 3


= 10000 + 9 + 600


= 10609


(iv) (704)2


We can also write it as;


(700 + 4)2


By using the formula (a + b)2 = a2 + b2 + 2ab


We get,


= (700 + 4)2 = (700)2 + (4)2 + 2 × 700 × 4


= 490000 + 16 + 5600


= 495616



Question 6.

Using the formula for squaring a binomial, evaluate the following:

(i) (69)2 (ii) (78)2

(iii) (197)2 (iv) (999)2


Answer:

(i) Given,


(69)2


We can also write it as;


(70 – 1)2


Now,


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


We get,


= (70 – 1)2 = (70)2 – 2 × 70 × 1 + (1)2


= 4900 – 140 + 1


= 4761


(ii) Given = (78)2


We can also write it as;


(80 – 2)2


Now,


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


We get,


(80 – 2)2 = (80)2 – 2 × 80 × 2 + (2)2


= 6400 – 320 + 4


= 6084


(iii) (197)2


We can also write it as;


(200 – 3)2


Now,


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


We get,


(200 – 3)2 = (200)2 – 2 × 200 × 3 + (3)2


= 40000 – 1200 + 9


= 38809


(iv) (999)2


We can also write it as;


(1000 – 1)2


Now,


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


We get,


(1000 - 1)2 = (1000)2 – 2 × 1000 × 1 + (1)2


= 1000000 – 2000 + 1


= 998001



Question 7.

Find the value of:

(i) (82)2 – (18)2

(ii) (128)2 – (72)2

(iii) 197 × 203

(iv)

(v) (14.7 × 15.3)

(vi)


Answer:

(i) Given,


(82)2 – (18)2


By using (a – b)(a + b) = a2 – b2


= (82 – 18)(82 + 18)


= (64)(100)


= 6400


(ii) (128)2 – (72)2


By using (a – b)(a + b) = a2 – b2


= (128 – 72)(128 + 72)


= (56)(200)


=11200


(iii) 197 × 203


By converting the given number into the form of formula we get,


= (200 – 3)(200 + 3)


= (200)2 –(3)2


= 40000 – 9


= 39991


(iv) Given,



By using the formula (a – b)(a + b) = a2 – b2


We get;




= 300


(v) (14.7 × 15.3)


By using (a – b)(a + b) = a2 – b2


We get;


= (15 – 0.3)(15 + 0.3)


= (15)2 – (0.3)2


= 225 – 0.09


= 224.91


(vi) (8.63)2 – (1.37)2


By using (a – b)(a + b) = a2 – b2


We get;


= (8.63 – 1.37)(8.63 + 1.37)


= (7.26)(10)


= 72.6



Question 8.

Find the value of the expression (9x2 + 24x + 16), when x = 12.


Answer:

Given,


(9x2 + 24x + 16)


x = 12


So, we can also write it as;


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


→ By the formula (a + b)2 we get,


= (3x + 4)2


= [3 (12) + 4]2


= [36 + 4]2


= [40]2 = 1600


Hence the value of the expression is 1600 when x =12.


Question 9.

Find the value of the expression (64x2 + 81y2 + 144xy), when x = 11 and .


Answer:

Given,


(64x2 + 81y2 + 144xy)


X = 11


Y =


By using the formula (a + b)2 we get;


= (8x)2 + (9y)2 + 2(8x)(9y)


= (8x + 9y)2


= [8(11) + 9 ]2


= (88 + 12)2


= (100)2 = 10000


Hence the value of the expression is 10000.



Question 10.

Find the value of the expression (36x2 + 25y2 – 60xy) when and


Answer:

Given,


(36x2 + 25y2 – 60xy)


X =


Y =


With the help of the formula (a - b)2 we get;


= (6x)2 + (5y)2 – 2(6x)(5y)


= (6x – 5y)2


=


= (4 – 1)2


= (3)2 = 9



Question 11.

If find the values of

(i) (ii)


Answer:

(i)


We know that,


From formula (a + b)2 = a2 + b2 + 2ab


=


=


So, by putting the values , we get,


= 42 =


=


(ii)


We know that,


From formula (a + b)2 = a2 + b2 + 2ab


=


=


So, by putting the values , we get,


= 142 =


=



Question 12.

If find the value of

(i) (ii)


Answer:

(i)


We know that,


From formula (a – b)2 = a2 + b2 – 2ab


=


=


So, by putting the values, we get,


= 52 =


=


(ii)


We know that,


From formula (a + b)2 = a2 + b2 + 2ab


=


=


So, by putting the values, we get,


= 272 =


=



Question 13.

Find the continued product:

(i) (x +1)(x – 1)(x2 + 1)

(ii) (x- 3)(x + 3)(x2 + 9)

(iii) (3x – 2y)(3x + 2y)(9x2 + 4y2)

(iv) (2p + 3)(2p – 3)(4p2 + 9)


Answer:

(i) (x +1)(x – 1)(x2 + 1)


We know that, from formula,


(a + b)(a – b) = a2 – b2


(x + 1)(x – 1) (x2 + 1) = (x2 – 1)(x2 + 1)


= (x2)2 – 1 = x4 – 1


(ii) (x- 3)(x + 3)(x2 + 9)


We know that, from formula,


(a + b)(a – b) = a2 – b2


(x – 3)(x + 3)(x2 + 9)


= (x2 – 9)(x2 + 9)


= (x2)2 – 92 = x4 – 81


(iii) (3x – 2y)(3x + 2y)(9x2 + 4y2)


We know that, from formula,


(a + b)(a – b) = a2 – b2


(3x – 2y)(3x + 2y)(9x2 + 4y2)


= (9x2 – 4y2)(9x2 + 4y2)


= 81x4 – 16y4


(iv) (2p + 3)(2p – 3)(4p2 + 9)


We know that, from formula,


(a + b)(a – b) = a2 – b2


(2p + 3)(2p – 3)(4p2 + 9)


= (4p2 – 9)(4p2+ 9)


= (4p2)2 – 92 = 16p4 – 81



Question 14.

If x + y = 12 and xy = 14, find the value of (x2 + y2).


Answer:

Given,


x + y = 12


Let’s square the both sides,


We get;


= (x + y)2 = (12)2


= x2 + y2 + 2xy = 144


= x2 + y2 = 144 – 2xy


Also given,


xy = 14


= x2 + y2 = 144 – 2(14)


= x2 + y2 = 144 – 28


= x2 + y2 = 116


So, the value of (x2 + y2) is 116.



Question 15.

If x – y = 7 and xy = 9, find the value of (x2 + y2).


Answer:

x – y = 7 (given)


By squaring both the sides we get;


= (x – y)2 = (7)2


= x2 + y2 – 2xy = 49


= x2 + y2 = 49 + 2xy


Also given,


xy = 9


= x2 + y2 = 49 + 2(9)


= x2 + y2 = 49 + 18


= x2 + y2 = 67


So, the value of x2 + y2 is 67.








Exercise 6e
Question 1.

The sum of (6a + 4b – c + 3), (2b – 3c + 4), (11b – 7a + 2c - 1) and (2c – 5a - 6) is
A.

B.

C.

D.


Answer:


Question 2.

(3q + 7p2 – 2r3 + 4) – (4p2 – 2q + 7r3 – 3) = ?
A.

B.

C.

D.


Answer:


After solving the bracket,


we get,


= 3q + 7p2 – 2r3 + 4 – 4p2 + 2q – 7r3 + 3 = 7p2 – 4p2 + 3q + 2q – 2r3 – 7r3 + 3 + 4


= 3p2 + 5q – 9r3 + 7


Question 3.

(x + 5) (x - 3) = ?
A. B.

C. D.


Answer:

After solving the equation,


we get,


(x + 5)(x – 3) = x(x – 3) + 5(x – 3)


= x2 – 3x + 5x – 15


= x2 + 2x – 15


Question 4.

(2x + 3)(3x - 1) = ?
A. B.

C. D.


Answer:

After solving the equations,


we get,


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


= 6x2 – 2x + 9x – 3


= 6x2 + 7x – 3


Question 5.

(x + 4)(x + 4) = ?
A. B.

C. D.


Answer:

We know that,


(x + 4)(x + 4) = (x + 4)2


From formula, (a + b)2 = a2 + b2 + 2ab


(x + 4)2 = x2 + 42 + 2 × x × 4


= x2 + 8x + 16


Question 6.

(x - 6)(x - 6) = ?
A. B.

C. D.


Answer: (x - 6)(x - 6)
By component wise multiplication
= x(x - 6) - 6(x - 6)
(from above we can see that, x.x = x2, x.(-6) = - 6x, -6.x = - 6x, and -6.-6 = +36)
= x2 - 6x - 6x + 36
= x2 - 12x + 36
Note: Multiplication of signs is given by-
(+) × (+) = +
(+) × (-) = -
(-)×(+)= -
(-) × (-) = +

Question 7.

(2x + 5)(2x - 5) = ?
A. B.

C. D.


Answer:

We know that,


From formula, (a + b)(a – b) = a2 – b2


(2x + 5)(2x – 5) = (2x)2 – (5)2


= 4x2 – 25


Question 8.

8a2b3 ÷ (- 2ab) = ?
A. B.

C. D.


Answer:

If we divide 8a2b3 by (-2ab)we get;


=


= - 4ab2


Question 9.

(2x2 + 3x + 1) ÷ (x + 1) = ?
A. B.

C. D.


Answer:

By dividing (2x2 + 3x + 1) by (x + 1)


We get;



Question 10.

(x2 - 4x + 4) ÷ (x - 2) = ?
A. B.

C. D.


Answer:

By dividing (x2 - 4x + 4) by (x - 2)


We get;



Question 11.

(a + 1)(a – 1)(a2 + 1) = ?
A. B.

C. D.


Answer:

We know that,


From formula, (a + b)(a – b) = a2 – b2


(a + 1)(a – 1)(a2 + 1) = (a2 – 1)(a2+ 1)


Again applying the formula,


(a2 – 1)(a2+ 1)
= (a2)2 – (12)2
= a4 – 1


Question 12.


A. B.

C. D.


Answer:

We know that,


From formula, (a + b)(a – b) = a2 – b2



Question 13.

If then
A. 25 B. 27

C. 23 B.


Answer:

We know that,


From formula, (a + b)2 = a2 + b2 + 2ab



……………….(i)


And


Putting value of in equation (i), we get,


(5)2 =


= 25 – 2 = 23.


Question 14.

If then
A. 36 B. 38

C. 32 D.


Answer:

We know that,


From formula, (a – b)2 = a2 + b2 – 2ab



……………….(i)


And


Putting value of in equation (i), we get,


(6)2 =


= 36+ 2= 38.


Question 15.

(82)2 – (18)2 = ?
A. 8218 B. 6418

C. 6400 D. 7204


Answer:

(82)2 – (18)2


By using (a – b)(a + b) = a2 – b2


= (82 – 18)(82 + 18)


= (64)(100)


= 6400


Question 16.

(197 × 203) = ?
A. 39991 B. 39999

C. 40009 D. 40001


Answer:

We can write following problem such as,


(197 × 203) = (200 – 3)(200 + 3)


From the formula, (a +b)(a – b) = a2 – b2


We get,


(200 – 3)(200 + 3) = 2002 – 32 = 40000 – 9 = 39991.


Question 17.

If (a + b) = 12 and ab = 14, then (a2 + b2) = ?
A.172

B. 116

C. 162

D. 126


Answer:

From the formula,


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


We get,


= a+ b = 12 and ab = 14


By putting values, we get,


122 = a2 + b2 + 2× 14


= a2 + b2 = 144 – 28 = 116.


Question 18.

If (a - b) = 7 and ab = 9, then (a2 + b2) = ?
A. 67 B. 31

C. 40 D. 58


Answer:

From the formula,


(a – b)2 = a2 + b2 –2ab


We get,


= a – b = 7 and ab = 9


By putting values, we get,


72 = a2 + b2 - 2× 9


= a2 + b2 = 49 + 18 = 67


Question 19.

If x = 10, then find the value of (4x2 + 20x + 25).
A. 256 B. 425

C. 625 D. 575


Answer:

(4x2 + 20x + 25)


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


We get;


= (2x)2 + (5)2 + 2(2x)(5)


= (2x + 5)2


= (2(10) + 5)2


= (20 + 5)2


= (25)2


= 625