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Factorisation

Class 8th Mathematics RS Aggarwal Solution
Exercise 7a
  1. (i) 12x + 15 (ii) 14m - 21 (iii) 9n - 12n^2 Factories:
  2. i. 16a^2 - 24ab ii. 15ab^2 - 20a^2 b iii. 12x^2 y^3 - 21x^3 y^2 Factories:…
  3. (i) 24x^3 - 36x^2 y (ii) 10x^3 - 15x^2 (iii) 36x^3 y - 60x^2 y^3 z Factories:…
  4. i. 9x^3 - 6x^2 + 12x ii. 8x^3 - 72xy + 12x iii. 18a^3 b^3 -27a^2 b^3 +36a^3 b^2…
  5. Factories: i. 14x^3 + 21x^4 y - 28x^2 y^2 ii. - 5 - 10t + 20t^2
  6. Factorise: i. x(x + 3) + 5(x + 3) ii. 5x(x 4) -7(x 4) iii. 2m(1 n) +3(1 n)…
  7. 6a(a - 2b) + 5b(a - 2b) Factories:
  8. x^3 (2a - b) + x^2 (2a - b) Factories:
  9. 9a(3a - 5b) - 12a^2 (3a - 5b) Factories:
  10. Factorize: (x + 5)^2 4(x + 5)
  11. 3(a - 2b)^2 -5(a - 2b) Factories:
  12. 2a + 6b - 3(a + 3b)^2 Factories:
  13. 16(2p - 3q)^2 - 4(2p - 3q) Factories:
  14. x(a - 3) + y(3 - a) Factories:
  15. 12(2x - 3y)^2 - 16(3y - 2x) Factories:
  16. (x + y)(2x + 5) - (x + y)(x + 3) Factories:
  17. ar + br + at + bt Factories:
  18. x^2 - ax - bx + ab Factories:
  19. ab^2 - bc^2 - ab + c^2 Factories:
  20. x^2 - xz + xy - yz Factories:
  21. 6ab - b^2 + 12ac - 2bc Factories:
  22. (x - 2y)^2 + 4x - 8y Factories:
  23. y^2 - xy(1 - x) - x^3 Factories:
  24. (ax + by)^2 + (bx - ay)^2 Factories:
  25. ab^2 + (a - 1)b -1 Factories:
  26. x^3 - 3x^2 + x - 3 Factories:
  27. ab(x^2 + y^2) - xy(a^2 + b^2) Factories:
  28. x^2 - x(a + 2b) + 2ab Factories:
Exercise 7b
  1. x^2 - 36 Factories:
  2. 4a^2 - 9 Factories:
  3. 81 - 49x^2 Factories:
  4. 4x^2 - 9y^2 Factories:
  5. 16a^2 - 225b^2 Factories:
  6. 9a^2 b^2 - 25 Factories:
  7. 16a^2 - 144 Factories:
  8. 63a^2 - 112b^2 Factories:
  9. 20a^2 - 45b^2 Factories:
  10. 12x^2 - 27 Factories:
  11. x^3 - 64x Factories:
  12. 16x^5 - 144x^3 Factories:
  13. 3x^5 - 48x^3 Factories:
  14. 16p^3 - 4p Factories:
  15. 63a^2 b^2 - 7 Factories:
  16. 1 - (b - c)^2 Factories:
  17. (2a + 3b)^2 - 16c^2 Factories:
  18. (2x + 5y)^2 - 1 Factories:
  19. 36c^2 - (5a + b)^2 Factories:
  20. (3x - 4y)^2 - 25z^2 Factories:
  21. x^2 - y^2 - 2y - 1 Factories:
  22. 25 - a^2 - b^2 - 2ab Factories:
  23. 25a^2 - 4b^2 + 28bc - 49c^2 Factories:
  24. 9a^2 - b^2 + 4b - 4 Factories:
  25. 100 - (x - 5)^2 Factories:
  26. Evaluate {(405)^2 - (395)^2 }
  27. Evaluate {(7.8)^2 - (2.2)^2 }.
Exercise 7c
  1. x^2 + 8x + 16 Factorize:
  2. x^2 + 14x + 49 Factorize:
  3. 1 + 2x + x^2 Factorize:
  4. 9 + 6z + z^2 Factorize:
  5. x^2 + 6ax + 9a^2 Factorize:
  6. 4y^2 + 20y + 25 Factorize:
  7. 36a^2 + 36a + 9 Factorize:
  8. 9m^2 + 24m + 16 Factorize:
  9. z^2 + z + 1/4 Factorize:
  10. 49a^2 + 84ab + 36b^2 Factorize:
  11. P^2 - 10p + 25 Factorize:
  12. 121a^2 - 88ab + 16b^2 Factorize:
  13. 1 - 6x + 9x^2 Factorize:
  14. 9y^2 - 12y + 4 Factorize:
  15. 16x^2 - 24x + 9 Factorize:
  16. m^2 - 4mn + 4n^2 Factorize:
  17. a^2 b^2 - 6ab + 9c^2 Factorize:
  18. m^4 + 2m^2 n^2 + n^4 Factorize:
  19. (l + m)^2 - 4lm Factorize:
Exercise 7d
  1. x^2 + 5x + 6 Factorize:
  2. y^2 + 10y + 24 Factorize:
  3. z^2 + 12z + 27 Factorize:
  4. p^2 + 6p + 8 Factorize:
  5. x^2 + 15x + 56 Factorize:
  6. y^2 + 19y + 60 Factorize:
  7. x^2 + 13x + 40 Factorize:
  8. q^2 - 10q + 21 Factorize:
  9. p^2 + 6p - 16 Factorize:
  10. x^2 - 10x + 24 Factorize:
  11. x^2 - 23x + 42 Factorize:
  12. Factorize: x^2 - 17x + 16
  13. y^2 - 21y + 90 Factorize:
  14. x^2 - 22x + 117 Factorize:
  15. x^2 - 9x + 20 Factorize:
  16. x^2 + x - 132 Factorize:
  17. x^2 + 5x - 104 Factorize:
  18. y^2 + 7y - 144 Factorize:
  19. z^2 + 19z - 150 Factorize:
  20. y^2 + y - 72 Factorize:
  21. a^2 + 6a - 91 Factorize:
  22. p^2 - 4p - 77 Factorize:
  23. x^2 - 7x - 30 Factorize:
  24. x^2 - 11x - 42 Factorize:
  25. x^2 - 5x - 24 Factorize:
  26. y^2 - 6y - 135 Factorize:
  27. z^2 - 12z - 45 Factorize:
  28. x^2 - 4x - 12 Factorize:
  29. 3x^2 + 10x + 8 Factorize:
  30. 3y^2 + 14y + 8 Factorize:
  31. 3z^2 - 10z + 8 Factorize:
  32. 2x^2 + x - 45 Factorize:
  33. 6p^2 + 11p - 10 Factorize:
  34. 2x^2 - 17x - 30 Factorize:
  35. 7y^2 - 19y - 6 Factorize:
  36. 28 - 31x - 5x^2 Factorize:
  37. Factorize: 3 + 23z - 8z^2
  38. 6x^2 - 5x - 6 Factorize:
  39. 3m^2 + 24m + 36 Factorize:
  40. 4n^2 - 8n + 3 Factorize:
  41. 6x^2 - 17x - 3 Factorize:
  42. 7x^2 - 19x - 6 Factorize:
Exercise 7e
  1. (7a^2 - 63b^2) =?A. (7a - 9b) (9a + 7b) B. (7a - 9b) (7a + 9b) C. 9(a - 3b) (a +…
  2. (2x - 32x^3) =?A. 2(x - 4) (x + 4) B. 2x(1 - 2x)^2 C. 2x(1 + 2x)^2 D. 2(1 - 4x)…
  3. X^3 - 144x =?A. x(x - 12)^2 B. x(x + 12)^2 C. x(x - 12) (x + 12) D. none of…
  4. 2 - 50x^2 =?A. 2(1 - 5x)^2 B. 2(1 + 5x)^2 C. (2 - 5x) (2 + 5x) D. 2(1 - 5x) (1 +…
  5. a^2 +bc+ab+ac =?A. (a + b) (a + c) B. (a + b) (b + c) C. (b + c) (c + a) D. a(a…
  6. pq^2 + q(p - 1) - 1 =?A. (pq + 1) (q - 1) B. p(q + 1) (q - 1) C. q(p - 1) (q +…
  7. ab - mn + an - bm =?A. (a-b)(m-n) B. (a-m)(b+n) C. (a-n)(m+b) D. (m-a)(n-b)…
  8. ab - a - b + 1= ?A. (a-1)(b-1) B. (1-a)(1-b) C. (a-1)(1-b) D. (1-a)(b-1)…
  9. x^2 - xz + xy - yz=?A. (x - z) (x + z) B. (x - y) (x - z) C. (x + y) (x - z) D.…
  10. 12m^2 - 27 =?A. (2m - 3) (3m - 9) B. 3(2m - 9) (3m - 1) C. 3(2m - 9) (2m + 1)…
  11. x^3 - x =?A. x(x^2 - x) B. x(x - x^2) C. x(1 + x) (1 - x) D. x(x + 1) (1 - x)…
  12. 1 - 2ab - (a^2 + b^2) =?A. (1 + a - b) (1 + a + b) B. (1 + a + b) (1 - a + b)…
  13. x^2 + 6x + 8=?A. (x + 3) (x + 5) B. x + 3) (x + 4) C. (x + 2) (x + 4) D. (x +…
  14. x^2 + 4x - 21=?A. (x - 7) (x + 3) B. (x + 7) (x - 3) C. (x - 7) (x - 3) D. (x +…
  15. y^2 + 2y - 3=?A. (y - 1) (y + 3) B. (y + 1) (y - 3) C. (y - 1) (y - 3) D. (y +…
  16. 40 + 3x - x^2 =?A. (5 + x) (x - 8) B. (5 - x) (8 + x) C. (5 + x) (8 - x) D. (5…
  17. 2x^2 + 5x + 3=?A. (x + 3) (2x + 1) B. (x + 1) (2x + 3) C. (2x + 5) (x - 3) D.…
  18. 6a^2 - 13a + 6=?A. (2a + 3) (3a - 2) B. (2a - 3) (3a + 2) C. (3a - 2) (2a - 3)…
  19. 4z^2 - 8z + 3=?A. (2z - 1) (2z - 3) B. (2z + 1) (3 - 2z) C. (2z + 3) (3z + 1)…
  20. 3 + 23y - 8y^2 =?A. (1 - 8y) (3 + y) B. (1 + 8y) (3 - y) C. (1 - 8y) (y - 3) D.…

Exercise 7a
Question 1.

Factories:

(i) 12x + 15

(ii) 14m – 21

(iii) 9n – 12n2


Answer:

(i) 12x + 15


Taking 3 as common from the whole, we get,


12x + 15 = 3(4x + 5).


(ii) 14m – 21,


Taking 7 as common from the whole, we get,


14m – 21 = 7(2m – 3)


(iii) 9n – 12n2,


Taking 3n as common from the whole, we get,


9n – 12n2 = 3n (3 – 4n).



Question 2.

Factories:

i. 16a2 – 24ab

ii. 15ab2 – 20a2b

iii. 12x2y3 – 21x3y2


Answer:

(i) Let’s take HCF of 16a2 – 24ab


Taking 8a as common from the whole, we get,


16a2 – 24ab = 8a(2a – 3b).


(ii) 15ab2 – 20a2b,


Taking 5ab as common from the whole, we get,


15ab2 – 20a2b = 5ab(3b – 4a)


(iii) 12x2y3 – 21x3y2,


Taking 3x2y2 as common from the whole, we get,


12x2y3 – 21x3y2 = 3x2y2(4y – 7x)



Question 3.

Factories:

(i) 24x3 – 36x2y

(ii) 10x3 – 15x2

(iii) 36x3y – 60x2y3z


Answer:

(i) 24x3 – 36x2y,


Taking 12x2 as common from the whole, we get,


24x3 – 36x2y = 12x2(2x – 3y)


(ii) 10x3 – 15x2


Taking 5x2 as common from the whole, we get,


10x3 – 15x2 = 5x2(2x – 3)


(iii) 36x3y – 60x2y3z


Taking 12x2y as common from the whole, we get,


36x3y – 60x2y3z = 12x2y(3x – 5y2z)



Question 4.

Factories:

i. 9x3 – 6x2 + 12x

ii. 8x3 – 72xy + 12x

iii. 18a3b3-27a2b3+36a3b2


Answer:

(i) Let’s find out the HCF of 9x3 , 6x2 , 12x



3x is the highest common factor which divides 9x3, 6x2 and 12x.


So,


9x3 – 6x2 + 12x = 3x(3x2 - 2x + 4)


(ii) Let’s find out the HCF of 8x3, 72xy and 12x



4x is the highest common factor which divides 8x3, 72xy and 12x.


So,


8x3 – 72xy + 12x = 4x(2x2 – 18y + 3)


(iii) Let’s find out the HCF of 18a3b3, 27a2b3, 36a3b2



9a2b2 is the highest common factor which divides 18a3b3, 27a2b3, 36a3b2.


So,


18a3b3 – 27a2b3 + 36a3b2 = 9a2b2 (2ab - 3b + 4a)



Question 5.

Factories:

i. 14x3 + 21x4y – 28x2y2

ii. - 5 – 10t + 20t2


Answer:

(i) Let’s find out the HCF of 14x3, 21x4y and 28x2y2



7x2 is the highest common factor of 14x3, 21x4y, 28x2y2


So,


14x3 + 21x4y – 28x2y2 = 7x2(2x + 3x2y – 4y2)


(ii) Let’s find out the HCF of 5, 10t and 20t2,



5 is the highest common factor of 5, 10t and 20t2.


So,


- 5 – 10t + 20t2 = - 5(1 + 2t – 4t2)


(Note: As we have learned in the previous chapter when we multiplied – sign with – sign it become +)



Question 6.

Factorise:
i. x(x + 3) + 5(x + 3)

ii. 5x(x – 4) -7(x – 4)

iii. 2m(1 – n) +3(1 – n)


Answer:

(i) x(x + 3) + 5(x + 3)

Taking x + 3 as common from the whole, we get,

(x + 3)(x + 5).

Hence, x(x + 3) + 5(x + 3) = (x + 3)(x + 5)

(ii) 5x(x – 4) -7(x – 4)

Taking x – 4 as common from the whole, we get,

5x(x – 4) -7(x – 4) = (x – 4)(5x – 7).


(iii) 2m(1 – n) +3(1 – n)


Taking 1 – n as common from the whole, we get,


2m(1 – n) +3(1 – n) = (1 – n)(2m + 3).


Question 7.

Factories:

6a(a – 2b) + 5b(a – 2b)


Answer:

6a(a – 2b) + 5b(a – 2b)


Taking a – 2b as common from the whole, we get,


= (a – 2b)(6a + 5b).



Question 8.

Factories:

x3(2a – b) + x2(2a – b)


Answer:

x3(2a – b) + x2(2a – b)


Taking 2a – b as common from the whole, we get,


= (2a – b)(x3 + x2).



Question 9.

Factories:

9a(3a – 5b) – 12a2(3a – 5b)


Answer:

9a(3a – 5b) – 12a2(3a – 5b)


Taking 3a – 5b as common from the whole, we get,


= (3a – 5b)(9a – 12a2).



Question 10.

Factorize:
(x + 5)2 – 4(x + 5)


Answer:

(x + 5)2 – 4(x + 5)

Taking (x + 5) as common from the whole, we get,

= (x + 5){(x + 5) – 4}

= (x + 5)(x + 5 – 4)

= (x + 5)(x + 1)

So,

The factors of (x + 5)2 – 4(x + 5) are: (x + 5) and (x + 1)


Question 11.

Factories:

3(a – 2b)2 -5(a – 2b)


Answer:

3(a – 2b)2 -5(a – 2b)


= (a – 2b) {3(a – 2b) – 5}


= (a – 2b){(3a – 6b) – 5}


= (a – 2b)(3a – 6b – 5)


So,


We get,


3(a – 2b)2 -5(a – 2b) = (a – 2b)(3a – 6b – 5)



Question 12.

Factories:

2a + 6b – 3(a + 3b)2


Answer:

2a + 6b – 3(a + 3b)2


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

= (a + 3b){2 - 3(a + 3b)}

= (a + 3b){2 - 3a - 9b}




Question 13.

Factories:

16(2p – 3q)2 – 4(2p – 3q)


Answer:

16(2p – 3q)2 – 4(2p – 3q)


= (2p – 3q){16(2p – 3q) – 4}


= (2p – 3q){(32p – 48q) – 4}


= (2p – 3q)(32p – 48q – 4)


= 4(2p – 3q)(8p – 12q -1)


So,


We get,


16(2p – 3q)2 – 4(2p – 3q) = 4(2p – 3q)(8p – 12q -1)



Question 14.

Factories:

x(a – 3) + y(3 – a)


Answer:

x(a – 3) + y(3 – a)


= x(a – 3) – y(a – 3)


= (a – 3)(x – y)



Question 15.

Factories:

12(2x – 3y)2 – 16(3y – 2x)


Answer:

12(2x – 3y)2 – 16(3y – 2x)


= 12(2x – 3y)2 + 16(2x -3y)


[Taking (2x - 3y) common from the expression]

= (2x – 3y) {12(2x – 3y) + 16}


= (2x – 3y)(24x – 36y + 16)


[Taking 4 common from the expression]

= 4(2x - 3y)(6x – 9y + 4)


So,


We get,


12(2x – 3y)2 – 16(3y – 2x) = 4(2x - 3y)(6x – 9y + 4)


Question 16.

Factories:

(x + y)(2x + 5) – (x + y)(x + 3)


Answer:

(x + y)(2x + 5) – (x + y)(x + 3)


= (x + y){(2x + 5) – (x + 3)}


= (x + y)(2x + 5 – x – 3)


= (x + y)(2x – x + 5 – 3)


= (x + y)(x + 2)


So,


We get,


(x + y)(2x + 5) – (x + y)(x + 3) = (x + y)(x + 2)



Question 17.

Factories:

ar + br + at + bt


Answer:

ar + br + at + bt


First group the terms together;


= (ar + br) + (at + bt)


= r(a + b) + t(a + b)


= (a + b)(r + t)


So,


We get,


ar + br + at + bt = (a + b)(r + t)



Question 18.

Factories:

x2 – ax – bx + ab


Answer:

x2 – ax – bx + ab


Let’s arrange the terms in a suitable form;


x2 – ax – bx + ab


= x2 – bx – ax + ab


= (x2 – bx) – (ax – ab)


= x(x – b) – a(x – b)


= (x – b)(x –a)


So we get,


x2 – ax – bx + ab = (x – b)(x –a)



Question 19.

Factories:

ab2 – bc2 – ab + c2


Answer:

ab2 – bc2 – ab + c2


Let’s first arrange the terms in a suitable form;


ab2 – bc2 – ab + c2


= ab2 – ab – bc2 + c2


= (ab2 – ab) – (bc2 - c2)


= ab(b – 1) – c2(b - 1)


= (b – 1)(ab – c2)


So we get,


ab2 – bc2 – ab + c2 = (b – 1)(ab – c2)



Question 20.

Factories:

x2 – xz + xy – yz


Answer:

Let’s first arrange the terms in a suitable form;


x2 – xz + xy – yz


= x2 + xy – xz – yz


= (x2 + xy) – (xz + yz)


= x(x + y) – z(x + y)


= (x + y)(x – z)


So we get,


x2 – xz + xy – yz = (x + y)(x – z)



Question 21.

Factories:

6ab – b2 + 12ac – 2bc


Answer:

6ab – b2 + 12ac – 2bc


= 6ab + 12ac – b2 – 2bc


= (6ab + 12ac) – (b2 + 2bc)


= 6a(b + 2c) – b(b + 2c)


= (b + 2c)(6a – b)


So we get,


6ab – b2 + 12ac – 2bc = (b + 2c)(6a – b)



Question 22.

Factories:

(x – 2y)2 + 4x – 8y


Answer:

(x – 2y)2 + 4x – 8y


= (x – 2y)2 + 4(x – 2y)


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


= (x -2y){(x -2y) +4}


= (x – 2y)(x – 2y + 4)


So we get,


(x – 2y)2 + 4x – 8y = = (x – 2y)(x – 2y + 4)



Question 23.

Factories:

y2 – xy(1 – x) – x3


Answer:

y2 – xy(1 – x) – x3


= y2 – xy + x2y – x3


= (y2 – xy) + (x2y – x3)


= y(y – x) + x2(y – x)


= (y –x)(y + x2)


So we get,


y2 – xy(1 – x) – x3 = (y –x)(y + x2)



Question 24.

Factories:

(ax + by)2 + (bx – ay)2


Answer:

(ax + by)2 + (bx – ay)2


By using the formulas;


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


(a – b)2 = a2 + b2 – 2ab


= (a2x2 + b2y2 + 2axby) + (b2x2 + a2y2 – 2bxay)


= a2x2 + a2y2 + b2y2 + b2x2 + 2axby – 2bxay


= a2(x2 + y2) + b2x2 + b2y2 + 2axby – 2axby


= a2(x2 + y2) + b2(x2 + y2)


= (x2 + y2)(a2 + b2)


So we get,


(ax + by)2 + (bx – ay)2 = (x2 + y2)(a2 + b2)



Question 25.

Factories:

ab2 + (a – 1)b -1


Answer:

ab2 + (a – 1)b -1


= ab2 + ba – b – 1


= (ab2 + ba) – (b + 1)


= ab (b + 1) - 1(b + 1)


= (b + 1)(ab – 1)


So we get,


ab2 + (a – 1)b -1 = (b + 1)(ab – 1)



Question 26.

Factories:

x3 – 3x2 + x – 3


Answer:

x3 – 3x2 + x – 3


= (x3 – 3x2) + (x -3)


= x2(x – 3) + 1(x – 3)


= (x – 3)(x2 + 1)


So we get,


x3 – 3x2 + x – 3 = (x – 3)(x2 + 1)



Question 27.

Factories:

ab(x2 + y2) – xy(a2 + b2)


Answer:

ab(x2 + y2) – xy(a2 + b2)


= abx2 + aby2 – a2xy – b2xy


= abx2 – a2xy + aby2 – b2xy


= ax(bx – ay) + by(ay – bx)


= ax(bx – ay) – by(bx – ay)


= (bx – ay)(ax – by)


So we get,


ab(x2 + y2) – xy(a2 + b2) = (bx – ay)(ax – by)



Question 28.

Factories:

x2 – x(a + 2b) + 2ab


Answer:

x2 – x(a + 2b) + 2ab


= x2 – ax – 2bx + 2ab


= x2 – 2bx – ax + 2ab


= (x2 – 2bx) – (ax – 2ab)


= x(x – 2b) – a(x – 2b)


= (x – 2b)(x – a)


So we get,


x2 – x(a + 2b) + 2ab = (x – 2b)(x – a)




Exercise 7b
Question 1.

Factories:

x2 – 36


Answer:

We have,


x2 – 36


Which is,


= (x)2 – (6)2


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


We get,


x2 – 36 = (x)2 – (6)2


= (x + 6)(x – 6)



Question 2.

Factories:

4a2 – 9


Answer:

We have,


4a2 – 9


= (2a)2 – (3)2


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


We get,


4a2 – 9 = (2a)2 – (3)2


= (2a + 3)(2a – 3)



Question 3.

Factories:

81 – 49x2


Answer:

We have,


81 – 49x2


= (9)2 – (7x)2


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


We get,


81 – 49x2 = (9)2 – (7x)2


= (9 + 7x)(9 – 7x)



Question 4.

Factories:

4x2 – 9y2


Answer:

We have,


4x2 – 9y2


= (2x)2 – (3y)2


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


We get,


4x2 – 9y2 = (2x)2 – (3y)2


= (2x + 3y)(2x – 3y)



Question 5.

Factories:

16a2 – 225b2


Answer:

We have,


16a2 – 225b2


= (4a)2 – (15b)2


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


We get,


16a2 – 225b2 = (4a)2 – (15b)2


= (4a + 15b)(4a – 15b)



Question 6.

Factories:

9a2b2 – 25


Answer:

We have,


9a2b2 – 25


= (3ab)2 – (5)2


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


We get,


9a2b2 – 25 = (3ab)2 – (5)2


= (3ab + 5)(3ab – 5)



Question 7.

Factories:

16a2 – 144


Answer:

We have,


16a2 – 144


= (4a)2 – (12)2


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


We get,


16a2 – 144 = (4a)2 – (12)2


= (4a + 12)(4a – 12)


= 4(a + 3) 4(a – 3)


= 16(a + 3)(a – 3)



Question 8.

Factories:

63a2 – 112b2


Answer:

We have,


63a2 – 112b2


= 7(9a2 – 16b2)


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


We get,


63a2 – 112b2 = 7(9a2 – 16b2)


= 7{(3a)2 – (4b)2}


= 7(3a + 4b)(3a – 4b)



Question 9.

Factories:

20a2 – 45b2


Answer:

We have,


20a2 – 45b2


= 5(4a2 – 9b2)


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


We get,


20a2 – 45b2 = 5(4a2 – 9b2)


= 5{(2a)2 – (3b)2}


= 5(2a + 3b)(2a – 3b)



Question 10.

Factories:

12x2 – 27


Answer:

We have,


12x2 – 27


= 3(4x2 – 9)


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


We get,


12x2 – 27 = 3(4x2 – 9)


= 3{(2x)2 – (3)2}


= 3(2x + 3)(2x – 3)



Question 11.

Factories:

x3 – 64x


Answer:

We have,


x3 – 64x


= x(x2 – 64)


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


We get,


x3 – 64x = x(x2 – 64)


= x{(x)2 – (8)2}


= x(x + 8)(x – 8)



Question 12.

Factories:

16x5 – 144x3


Answer:

We have,


16x5 – 144x3


= 3x3(x2 – 9)


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


We get,


16x5 – 144x3 = 3x3(x2 – 9)


= 16x3{(x)2 – (3)2}


= 16x3(x + 3)(x – 3)



Question 13.

Factories:

3x5 – 48x3


Answer:

We have,


3x5 – 48x3


= 3x3(x2 – 16)


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


We get,


3x5 – 48x3 = 3x3(x2 – 16)


= 3x3{(x)2 – (4)2}


= 3x3(x + 4)(x – 4)



Question 14.

Factories:

16p3 – 4p


Answer:

We have,


16p3 – 4p


= 4p(4p2 – 1)


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


We get,


16p3 – 4p = 4p(4p2 – 1)


= 4p{(2p)2 – (1)2}


= 4p(2p + 1)(2p – 1)



Question 15.

Factories:

63a2b2 – 7


Answer:

We have,


63a2b2 – 7


= 7(9a2b2 – 1)


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


We get,


63a2b2 – 7 = 7(9a2b2 – 1)


= 7{(3ab)2 – (1)2}


= 7(3ab + 1)(3ab – 1)



Question 16.

Factories:

1 – (b – c)2


Answer:

We have,


1 – (b – c)2


= (1)2 – (b –c)2


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


We get,


1 – (b – c)2 = (1)2 – (b –c)2


= {1 + (b – c)}{1 – (b – c)}


= (1 + b – c)(1 – b + c)



Question 17.

Factories:

(2a + 3b)2 – 16c2


Answer:

Given,


(2a + 3b)2 – 16c2


= (2a + 3b)2 – (4c)2


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


We get,


(2a + 3b)2 – 16c2 = (2a + 3b)2 – (4c)2


= {(2a + 3b) + 4c}{(2a + 3b) – 4c}


= (2a + 3b + 4c)(2a + 3b – 4c)



Question 18.

Factories:

(2x + 5y)2 – 1


Answer:

Given,


(2x + 5y)2 – (1)2


= (2x + 5y)2 – (1)2


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


We get,


(2x + 5y)2 – (1)2 = (2x + 5y)2 – (1)2


= {(2x + 5y) + 1}{(2x + 5y) – 1}


= (2x + 5y + 1)(2x + 5y – 1)



Question 19.

Factories:

36c2 – (5a + b)2


Answer:

Given,


36c2 – (5a + b)2


= (6c)2 – (5a + b)2


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


We get,


36c2 – (5a + b)2 = (6c)2 – (5a + b)2


= {(6c) + (5a + b)}{(6c) – (5a + b)}


= (6c + 5a + b)(6c – 5a – b)



Question 20.

Factories:

(3x – 4y)2 – 25z2


Answer:

Given,


(3x – 4y)2 – 25z2


= (3x – 4y)2 – (5z)2


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


We get,


(3x – 4y)2 – 25z2 = (3x – 4y)2 – (5z)2


={(3x – 4y) + 5z}{(3x – 4y) – 5z}


= (3x – 4y + 5z)(3x – 4y – 5z)



Question 21.

Factories:

x2 – y2 – 2y – 1


Answer:

Given,


x2 – y2 – 2y – 1


= x2 – (y2 + 2y + 1)


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


We get,


x2 – y2 – 2y – 1 = x2 – (y2 + 2y + 1)


= (x)2 – (y + 1)2


={x + (y +1)}{x – (y + 1)}


= (x + y + 1)(x – y – 1)



Question 22.

Factories:

25 – a2 – b2 – 2ab


Answer:

Given,


25 – a2 – b2 – 2ab


= 25 – (a2 + b2 + 2ab)


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


We get,


25 – a2 – b2 – 2ab = 25 – (a2 + b2 + 2ab)


= 25 – (a + b)2


=(5)2 – (a + b)2


= {5 + (a + b)}{5 – (a + b)}


= (5 + a + b)(5 – a – b)



Question 23.

Factories:

25a2 – 4b2 + 28bc – 49c2


Answer:

Given,


25a2 – 4b2 + 28bc – 49c2


= 25a2 – (4b2 – 28bc + 49c2)


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


We get,


25a2 – 4b2 + 28bc – 49c2 = 25a2 – (4b2 – 28bc + 49c2)


= (5a)2 – (2b – 7c)2


= {5a + (2b – 7c)}{5a – (2b – 7c)}


= (5a + 2b – 7c)(5a – 2b + 7c)



Question 24.

Factories:

9a2 – b2 + 4b – 4


Answer:

Given,


9a2 – b2 + 4b – 4


= 9a2 – (b2 – 4b + 4)


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


We get,


9a2 – b2 + 4b – 4 = 9a2 – (b2 – 4b + 4)


= (3a)2 – (b – 2)2


= {3a + (b – 2)}{3a – (b – 2)}


= (3a + b - 2)(3a – b + 2)



Question 25.

Factories:

100 – (x – 5)2


Answer:

Given,


100 – (x – 5)2


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


We get,


100 – (x – 5)2 = (10)2 – (x – 5)2


= {10 + (x – 5)}{10 – (x – 5)}


= (10 + x - 5)(10 – x + 5)


= (5 + x)(15 – x)



Question 26.

Evaluate {(405)2 – (395)2}


Answer:

Given,


{(405)2 – (395)2}


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


We get,


{(405)2 – (395)2} = (405 + 395)(405 – 395)


= (800 × 10)


= 8000



Question 27.

Evaluate {(7.8)2 – (2.2)2}.


Answer:

We have,


{(7.8)2 – (2.2)2}


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


We get,


{(7.8)2 – (2.2)2} = (7.8 + 2.2)(7.8 – 2.2)


= (10 × 5.6)


= 56


So,


{(7.8)2 – (2.2)2} = 56




Exercise 7c
Question 1.

Factorize:

x2 + 8x + 16


Answer:

Given,


x2 + 8x + 16


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


We get,


= x2 + 2 × (x) × 4 + (4)2


= (x + 4)2



Question 2.

Factorize:

x2 + 14x + 49


Answer:

Given;


x2 + 14x + 49


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


We get,


= x2 + 2 × (x) × 7 + (7)2


= (x + 7)2



Question 3.

Factorize:

1 + 2x + x2


Answer:

Given,


1 + 2x + x2 = x2 + 2x + 1


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


We get,


= x2 + 2 × (x) × 1 + (1)2


= (x + 1)2


= (x + 1)(x + 1)

Question 4.

Factorize:

9 + 6z + z2


Answer:

Given,


9 + 6z + z2 = z2 + 6z + 9


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


We get,


= z2 + 2 × z × 3 + (3)2


= (3 + z)2



Question 5.

Factorize:

x2 + 6ax + 9a2


Answer:

Given;


x2 + 6ax + 9a2


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


We get,


= x2 + 2 × (x) × 3a + (3a)2


= (x + 3a)2



Question 6.

Factorize:

4y2 + 20y + 25


Answer:

Given;


4y2 + 20y + 25


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


We get,


= (2y)2 + 2 × 2y × 5 + (5)2


= (2y + 5)2



Question 7.

Factorize:

36a2 + 36a + 9


Answer:

Given,


36a2 + 36a + 9


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


We get,


= (6a)2 + 2×6a×3 + (3)2


= (6a + 3)2



Question 8.

Factorize:

9m2 + 24m + 16


Answer:

Given,


9m2 + 24m + 16


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


We get,


= (3m)2 + 2×3m×4 + (4)2


= (3m + 4)2



Question 9.

Factorize:



Answer:

Given,



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


We get,





Question 10.

Factorize:

49a2 + 84ab + 36b2


Answer:

Given,


49a2 + 84ab + 36b2


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


We get,


= (7a)2 + 2 × 7a × 6b + (6b)2


= (7a + 6b)2



Question 11.

Factorize:

P2 – 10p + 25


Answer:

Given,


P2 – 10p + 25


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


We get,


= p2 – 2 × p × 5 + (5)2


= (p – 5)2



Question 12.

Factorize:

121a2 – 88ab + 16b2


Answer:

Given,


121a2 – 88ab + 16b2


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


We get,


= (11a)2 – 2 × 11a × 4b + (4b)2


= (11a – 4b)2



Question 13.

Factorize:

1 – 6x + 9x2


Answer:

Given,


1 – 6x + 9x2 = 9x2 – 6x + 1


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


We get,


= (3x)2 – 2 × (3x) × 1 + (1)2


= (3x – 1)2



Question 14.

Factorize:

9y2 – 12y + 4


Answer:

Given,


9y2 – 12y + 4


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


We get,


= (3y)2 – 2 × 3y × 2 + (2)2


= (3y – z)2



Question 15.

Factorize:

16x2 – 24x + 9


Answer:

Given,


16x2 – 24x + 9


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


= (4x)2 – 2 × (4x) × 3 + (3)2


= (4x – 3)2



Question 16.

Factorize:

m2 – 4mn + 4n2


Answer:

Given,


m2 – 4mn + 4n2


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


= m2 - 2×m×2n + (2n)2


= (m – 2n)2



Question 17.

Factorize:

a2b2 – 6ab + 9c2


Answer:

Given,


a2b2 – 6ab + 9c2


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


We get,


= (ab)2 - 2×ab×3c + (3c)2


= (ab – 3c)2



Question 18.

Factorize:

m4 + 2m2n2 + n4


Answer:

Given,


m4 + 2m2n2 + n4


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


We get,


= (m2)2 + 2×m2×n2 + (n2)2


= (m2 + n2)



Question 19.

Factorize:

(l + m)2 – 4lm


Answer:

Given,


(l + m)2 – 4lm


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


We get,


(l + m)2 – 4lm = (l2 + m2 + 2lm) – 4lm


= l2 + m2 + 2lm – 4lm


= l2 + m2 – 2lm


= (l)2 + (m)2 - 2×l×m


= (l – m)2




Exercise 7d
Question 1.

Factorize:

x2 + 5x + 6


Answer:

Given,


x2 + 5x + 6


Now first find the numbers whose-


Sum = 5 and


Product = 6


Required numbers are 2 and 3,


So we get;


x2 + 5x + 6


= x2 + 2x + 3x + 6


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


= (x + 2)(x + 3)



Question 2.

Factorize:

y2 + 10y + 24


Answer:

Given,


y2 + 10y + 24


Now first find the numbers whose-


Sum = 10 and


Product = 24


Required numbers are 6 and 4,


So we get;


y2 + 10y + 24 = y2 + 6y + 4y + 24


= y(y + 6) + 4(y + 6)


= (y + 6)(y + 4)



Question 3.

Factorize:

z2 + 12z + 27


Answer:

z2 + 12z + 27


Now first find the numbers whose-


Sum = 12 and


Product = 27


Required numbers are 9 and 3,


So we get;


z2 + 12z + 27


= z2 + 9z + 3z + 27


= z(z + 9) + 3(z + 9)


= (z + 9)(z + 3)



Question 4.

Factorize:

p2 + 6p + 8


Answer:

Given,


p2 + 6p + 8


Now first find the numbers whose-


Sum = 6 and


Product = 8


Required numbers are 4 and 2,


So we get;


p2 + 6p + 8


= p2 + 4p + 2p + 8


= p(p + 4) + 2(p + 4)


= (p + 4)(p + 2)



Question 5.

Factorize:

x2 + 15x + 56


Answer:

Given,


x2 + 15x + 56


Now first find the numbers whose-


Sum = 15 and


Product = 56


Required numbers are 7 and 8,


So we get;


x2 + 15x + 56


= x2 + 7x + 8x + 56


= x(x + 7) + 8(x + 7)


= (x + 7)(x + 8)



Question 6.

Factorize:

y2 + 19y + 60


Answer:

y2 + 19y + 60


Now first find the numbers whose-


Sum = 19 and


Product = 60


Required numbers are 15 and 4,


So we get;


y2 + 19y + 60


= y2 + 15y + 4y + 60


= y(y + 15) + 4(y + 15)


= (y + 15)(y + 4)



Question 7.

Factorize:

x2 + 13x + 40


Answer:

Given,


x2 + 13x + 40


Now first find the numbers whose-


Sum = 13 and


Product = 40


Required numbers are 8 and 5,


So we get;


x2 + 13x + 40


= x2 + 8x + 5x + 40


= x(x + 8) + 5(x + 8)


= (x + 8)(x + 5)



Question 8.

Factorize:

q2 – 10q + 21


Answer:

Given,


q2 – 10q + 21


Now first find the numbers whose-


Sum = - 10 and


Product = 21


Required numbers are 7 and 3,


So we get;


q2 – 10q + 21


= q2 – 7q – 3q + 21


= q(q – 7) – 3(q – 7)


= (q – 7)(q – 3)



Question 9.

Factorize:

p2 + 6p – 16


Answer:

Given,


p2 + 6p – 16


Now first find the numbers whose-


Sum = 6 and


Product = - 16


Required numbers are 8 and 2,


So we get;


p2 + 6p – 16


= p2 + 8p – 2p – 16


= p(p + 8) – 2(p + 8)


= (p + 8)(p – 2)



Question 10.

Factorize:

x2 – 10x + 24


Answer:

Given,


x2 – 10x + 24


Now first find the numbers whose-


Sum = - 10 and


Product = 24


Required numbers are 6 and 4,


So we get;


x2 – 10x + 24


= x2 – 6x – 4x + 24


= x(x – 6) – 4(x – 6)


= (x – 6)(x – 4)



Question 11.

Factorize:

x2 – 23x + 42


Answer:

Given,


x2 – 23x + 42


Now, first we have to find out the numbers whose-


Sum = - 23 and


Product = 42


The numbers are 21 and 2,


So,


x2 – 23x + 42 = x2 – 21x – 2x + 42


= x(x – 21) – 2(x – 21)


= (x – 21)(x – 2)



Question 12.

Factorize:

x2 – 17x + 16


Answer:

Given,


x2 – 17x + 16


Now, first we have to find out the numbers whose-


Sum = - 17 and


Product = 16


The numbers are 16 and 1,


So,


x2 – 17x + 16 = x2 – 16x – 1x + 16


= x(x – 16) – 1(x – 16)


= (x – 16)(x – 1)



Question 13.

Factorize:

y2 – 21y + 90


Answer:

Given,


y2 – 21y + 90


Now, first we have to find out the numbers whose-


Sum = - 21 and


Product = 90


The numbers are 15 and 6,


So,


y2 – 21y + 90 = y2 – 15y – 6y + 90


= y(y – 15) – 6(y – 15)


= (y – 15)(y – 6)



Question 14.

Factorize:

x2 – 22x + 117


Answer:

Given,


x2 – 22x + 117


Now, first we have to find out the numbers whose-


Sum = - 22 and


Product = 117


The numbers are 13 and 9,


So,


x2 – 22x + 117 = x2 – 13x – 9x + 117


= x(x – 13) – 9(x – 13)


= (x – 13)(x – 9)



Question 15.

Factorize:

x2 – 9x + 20


Answer:

x2 – 9x + 20


Now, first we have to find out the numbers whose-


Sum = - 9 and


Product = 20


The numbers are 5 and 4,


So,


x2 – 9x + 20 = x2 – 5x – 4x + 20


= x(x – 5) – 4(x – 5)


= (x – 5)(x – 4)



Question 16.

Factorize:

x2 + x – 132


Answer:

x2 + x – 132


Now, first we have to find out the numbers whose-


Sum = 1 and


Product = - 132


The numbers are 12 and 11,


So,


x2 + x – 132 = x2 + 12x – 11x – 132


= x(x + 12) – 11(x + 12)


= (x + 12)(x – 11)



Question 17.

Factorize:

x2 + 5x – 104


Answer:

x2 + 5x – 104


Now, first we have to find out the numbers whose-


Sum = 5 and


Product = - 104


The numbers are 13 and 8,


So,


x2 + 5x – 104 = x2 + 13x – 8x – 104


= x(x + 13) – 8(x + 13)


= (x + 13)(x – 8)



Question 18.

Factorize:

y2 + 7y – 144


Answer:

y2 + 7y – 144


Now, first we have to find out the numbers whose-


Sum = 7 and


Product = - 144


The numbers are 16 and - 9,


So,


y2 + 7y – 144


= y2 + 16y – 9y – 144


= y(y + 16) – 9(y + 16)


= (y + 16)(y – 9)



Question 19.

Factorize:

z2 + 19z – 150


Answer:

Given,


z2 + 19z – 150


Now, first we have to find out the numbers whose-


Sum = 19 and


Product = - 150


The numbers are 25 and 6,


So,


z2 + 19z – 150


= z2 + 25z – 6z – 150


= z(z + 25) – 6(z + 25)


= (z + 25)(z – 6)



Question 20.

Factorize:

y2 + y – 72


Answer:

Given,


y2 + y – 72


Now, first we have to find out the numbers whose-


Sum = 1 and


Product = - 72


The numbers are 9 and 8,


So,


y2 + y – 72


= y2 + 9y – 9y – 72


= y(y + 9) – 9(y + 9)


= (y + 9)(y – 9)



Question 21.

Factorize:

a2 + 6a – 91


Answer:

a2 + 6a – 91


Now, first we have to find out the numbers whose-


Sum = 6 and


Product = - 91


The numbers are 13 and 7,


So,


a2 + 6a – 91


= a2 + 13a – 7a – 91


= a(a + 13) – 7(a + 13)


= (a + 13) (a – 7)



Question 22.

Factorize:

p2 – 4p – 77


Answer:

p2 – 4p – 77


Now, first we have to find out the numbers whose-


Sum = - 4 and


Product = - 77


The numbers are 11 and 7,


So,


p2 – 4p – 77


= p2 – 11p + 7p – 77


= p(p – 11) + 7(p – 11)


= (p – 11)(p + 7)



Question 23.

Factorize:

x2 – 7x – 30


Answer:

x2 – 7x – 30


Now, first we have to find out the numbers whose-


Sum = - 7 and


Product = - 30


The numbers are 10 and 3,


So,


x2 – 7x – 30


= x2 – 10x + 3x – 30


= x(x – 10) + 3(x – 10)


= (x – 10)(x + 3)



Question 24.

Factorize:

x2 – 11x – 42


Answer:

x2 – 11x – 42


Now, first we have to find out the numbers whose-


Sum = - 11 and


Product = - 42


The numbers are 14 and 3,


So,


x2 – 11x – 42


= x2 – 14x + 3x – 42


= x(x – 14) + 3(x + 14)


= (x – 14)(x + 3)



Question 25.

Factorize:

x2 – 5x – 24


Answer:

x2 – 5x – 24


Now, first we have to find out the numbers whose-


Sum = - 5 and


Product = - 24


The numbers are - 8 and 3,


So,


x2 – 5x – 24


= x2 – 8x + 3x – 24


= x(x – 8) + 3(x – 8)


= (x – 8)(x + 3)



Question 26.

Factorize:

y2 – 6y – 135


Answer:

Given;


y2 – 6y – 135


Now first find the numbers whose-


Sum = - 6 and


Product = - 135


Required numbers are 15 and 9,


So we get;


y2 – 6y – 135


= y2 – 15y + 9y – 135


= y(y – 15) + 9(y – 15)


= (y – 15)(y + 9)



Question 27.

Factorize:

z2 – 12z – 45


Answer:

Given


z2 – 12z – 45


Now first find the numbers whose-


Sum = - 12 and


Product = - 45


Required numbers are 15 and 3,


So we get;


z2 – 12z – 45


= z2 – 15z + 3z - 45


= z(z – 15) + 3(z – 15)


= (z – 15)(z + 3)



Question 28.

Factorize:

x2 – 4x – 12


Answer:

Given,


x2 – 4x – 12


Now first find the numbers whose-


Sum = - 4 and


Product = - 12


Required numbers are 6 and 2,


So we get;


x2 – 4x – 12


= x2 – 6x + 2x – 12


= x(x – 6) + 2(x – 6)


= (x – 6)(x + 2)



Question 29.

Factorize:

3x2 + 10x + 8


Answer:

Given,


3x2 + 10x + 8


Now first find the numbers whose-


Sum = 10 and


Product = 3 × 8 = 24


Required numbers are 6 and 4,


So we get;


3x2 + 10x + 8


= 3x2 + 6x + 4x + 8


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


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



Question 30.

Factorize:

3y2 + 14y + 8


Answer:

Given,


3y2 + 14y + 8


Now first find the numbers whose-


Sum = 14 and


Product = 3 × 8 = 24


Required numbers are 12 and 2,


So we get;


3y2 + 14y + 8 = 3y2 + 12y + 2y + 8


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


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



Question 31.

Factorize:

3z2 – 10z + 8


Answer:

Given,


3z2 – 10z + 8


Now, first we have to find out the numbers whose-


Sum = - 10 and


Product = 3 × 8 = 24


The numbers are 6 and 4,


So,


3z2 – 10z + 8


= 3z2 – 6z – 4z + 8


= 3z(z – 2) – 4(z – 2)


= (z – 2)(3z – 4)



Question 32.

Factorize:

2x2 + x – 45


Answer:

Given,


2x2 + x – 45


Now first find the numbers whose-


Sum = 1 and


Product = - 45 × 2 = - 90


Required numbers are 10 and 9,


So we get;


2x2 + x – 45


= 2x2 + 10x – 9x – 45


= 2x(x + 5) – 9(x + 5)


= (x + 5)(2x – 9)



Question 33.

Factorize:

6p2 + 11p – 10


Answer:

Given,


6p2 + 11p – 10


Now first find the numbers whose-


Sum = 11 and


Product = - 10 × 6 = - 60


Required numbers are 15 and 4,


So we get;


= 6p2 + 15p – 4p – 10


= 3p(2p + 5) – 2(2p + 5)


= (2p + 5)(3p – 2)



Question 34.

Factorize:

2x2 – 17x – 30


Answer:

Given,


2x2 – 17x – 30


Now first find the numbers whose-


Sum = - 17 and


Product = - 30 × 2 = - 60


Required numbers are 20 and 3,


So we get;


2x2 – 17x – 30


= 2x2 – 20x + 3x – 30


= 2x(x – 10) + 3(x – 10)


= (x – 10)(2x + 3)



Question 35.

Factorize:

7y2 – 19y – 6


Answer:

Given,


7y2 – 19y – 6


Now first find the numbers whose-


Sum = - 19 and


Product = - 6 × 7 = - 42


Required numbers are 21 and 2,


So we get;


7y2 – 19y – 6


= 7y2 – 21y + 2y – 6


= 7y(y – 3) + 2(y – 3)


= (y – 3)(7y + 2)



Question 36.

Factorize:

28 – 31x – 5x2


Answer:

Given,


28 – 31x – 5x2


Now first find the numbers whose-


Sum = - 31 and


Product = - 5 × 28 = 140


Required numbers are 35 and 4,


So we get;


28 – 31x – 5x2


= 28 + 4x – 35x – 5x2


= 4(7 + x) – 5x(7 + x)


= (7 + x)(4 – 5x)



Question 37.

Factorize:

3 + 23z – 8z2


Answer:

Given,


3 + 23z – 8z2


Now first find the numbers whose-


Sum = 23 and


Product = - 8 × 3 = 24


Required numbers are 24 and 1,


So we get;


3 + 23z – 8z2


= 3 + 24z – z – 8z2


= 3(1 + 8z) – z(1 + 8z)


= (1 + 8z)(3 – z)



Question 38.

Factorize:

6x2 – 5x – 6


Answer:

Given,


6x2 – 5x – 6


Now first find the numbers whose-


Sum = - 5 and


Product = - 6 × 6 = - 36


Required numbers are 9 and 4,


So we get;


= 6x2 – 9x + 4x – 6


= 3x(2x – 3) + 2(2x – 3)


= (2x – 3)(3x + 2)



Question 39.

Factorize:

3m2 + 24m + 36


Answer:

Given,


3m2 + 24m + 36


Now first find the numbers whose-


Sum = 24 and


Product = 36 × 3 = 108


Required numbers are 18 and 6,


So we get;


3m2 + 24m + 36


= 3m2 + 18m + 6m + 36


= 3m(m + 6) + 6(m + 6)


= (m + 6)(3m + 6)



Question 40.

Factorize:

4n2 – 8n + 3


Answer:

Given,


4n2 – 8n + 3


Now first find the numbers whose-


Sum = - 8 and


Product = 4 × 3 = 12


Required numbers are 6 and 2,


So we get;


4n2 – 8n + 3


= 4n2 – 2n – 6n + 3


= 2n(2n – 1) – 3(2n – 3)


= (2n – 1)(2n – 3)



Question 41.

Factorize:

6x2 – 17x – 3


Answer:

Given,


6x2 – 17x – 3


Now, first we have to find out the numbers whose-


Sum = - 17 and


Product = 6 × - 3 = - 18


The numbers are 18 and 1,


So,


6x2 – 17x – 3


= 6x2 – 18x + 1x – 3


= 6x(x – 3) + 1(x – 3)


= (x – 3)(6x + 1)



Question 42.

Factorize:

7x2 – 19x – 6


Answer:

Given,


7x2 – 19x – 6


Now, first we have to find out the numbers whose-


Sum = - 19 and


Product = 7 × - 6 = - 42


The numbers are 21 and 2,


So,


7x2 – 19x – 6


= 7x2 – 21x + 2x – 6


= 7x(x – 3) + 2(x – 3)


= (x – 3)(7x + 2)




Exercise 7e
Question 1.

(7a2 – 63b2) =?
A. (7a – 9b) (9a + 7b)

B. (7a – 9b) (7a + 9b)

C. 9(a - 3b) (a + 3b)

D. 7(a - 3b) (a + 3b)


Answer:

(7a2 – 63b2) = 7(a2 – 9b2) (taking 7 as common from whole)


= 7(a – 3b)(a + 3b) a2 – b2 = (a – b)(a + b)


Question 2.

(2x – 32x3) =?
A. 2(x – 4) (x + 4)

B. 2x(1 – 2x)2

C. 2x(1 + 2x)2

D. 2(1 – 4x) (1 + 4x)


Answer:

(2x – 32x3) = 2x(1 – 16x2) (taking 2x as common from whole)


= 2x(1 – 4x)(1 + 4x) a2 – b2 = (a – b)(a + b)


Question 3.

X3 – 144x =?
A. x(x – 12)2

B. x(x + 12)2

C. x(x – 12) (x + 12)

D. none of these


Answer:

X3 – 144x = x(x2 – 144) (taking x as common from whole)


= x(x – 12)(x + 12) a2 – b2 = (a – b)(a + b)


Question 4.

2 – 50x2=?
A. 2(1 – 5x)2

B. 2(1 + 5x)2

C. (2 – 5x) (2 + 5x)

D. 2(1 – 5x) (1 + 5x)


Answer:

2 – 50x2= 2(1 – 25x2) (taking 2 as common from whole)


= 2(1 – 5x)(1 + 5x) a2 – b2 = (a – b)(a + b)


Question 5.

a2+bc+ab+ac =?
A. (a + b) (a + c)

B. (a + b) (b + c)

C. (b + c) (c + a)

D. a(a + b + c)


Answer:

a2+bc+ab+ac = a2+ab + bc + ac


Rearranging the terms and taking a and c as common respectively.


= a(a + b) + c(a + b)


= (a + c)(a + b).


Question 6.

pq2 + q(p – 1) – 1 =?
A. (pq + 1) (q - 1)

B. p(q + 1) (q - 1)

C. q(p - 1) (q + 1)

D. (pq - 1) (q + 1)


Answer:

pq2 + q(p – 1) – 1 = pq2 + qp – q – 1


= pq(q + 1) – 1(q + 1)


= (pq – 1)(q + 1)


Question 7.

ab – mn + an – bm =?
A. (a-b)(m-n)

B. (a-m)(b+n)

C. (a-n)(m+b)

D. (m-a)(n-b)


Answer:

= ab – mn + an – bm = ab + an – mn – bm


= a(b + n) – m(n + b)


= (a – m)(b + n).


Question 8.

ab – a – b + 1= ?
A. (a-1)(b-1)

B. (1-a)(1-b)

C. (a-1)(1-b)

D. (1-a)(b-1)


Answer:

ab – a – b + 1


= a(b – 1) – 1(b – 1) (taking a and – 1 as common )


= (a – 1)(b – 1).


Question 9.

x2 – xz + xy – yz=?
A. (x – z) (x + z)

B. (x – y) (x – z)

C. (x + y) (x – z)

D. (x – z) (z – x)


Answer:

= x2 – xz + xy – yz


= x(x – z) +y(x – z) (taking x and y as common resp.)


= (x + y)(x – z).


Question 10.

12m2 – 27 =?
A. (2m – 3) (3m – 9)

B. 3(2m – 9) (3m – 1)

C. 3(2m – 9) (2m + 1)

D. none of these


Answer:

12m2 – 27 = 3(4m2 – 9) (taking 3 as common from whole)


= 3(2m – 3)(2m + 3) a2 – b2 = (a – b)(a + b)


Question 11.

x3 – x =?
A. x(x2 – x)

B. x(x – x2)

C. x(1 + x) (1 – x)

D. x(x + 1) (1 – x)


Answer:

x3 – x = x(x2 – 1) (taking x as common from whole)


= x(x – 1)(x + 1) a2 – b2 = (a – b)(a + b)


Question 12.

1 – 2ab – (a2 + b2) =?
A. (1 + a - b) (1 + a + b)

B. (1 + a + b) (1 - a + b)

C. (1 + a + b) (1 - a - b)

D. (1 + a - b) (1 - a + b)


Answer:

1 – 2ab – (a2 + b2) = 1 – 2ab – a2 – b2


= 1 – (2ab + a2 + b2)


= 1 – (a + b)2


= (1 – a – b)(1 + a + b) a2 – b2 = (a – b)(a + b)


Question 13.

x2 + 6x + 8=?
A. (x + 3) (x + 5)

B. x + 3) (x + 4)

C. (x + 2) (x + 4)

D. (x + 1) (x + 8)


Answer:

x2 + 6x + 8


Factorizing the equation and taking x and 2 as common,


= x2 + 4x + 2x + 8


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


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


Question 14.

x2 + 4x – 21=?
A. (x - 7) (x + 3)

B. (x + 7) (x - 3)

C. (x - 7) (x - 3)

D. (x + 7) (x + 3)


Answer:

x2 + 4x – 21


Factorizing the equation and taking x and – 3 as common,


= x2 + 7x – 3x – 21


= x(x + 7) – 3(x + 7)


= (x – 3)(x + 7).


Question 15.

y2 + 2y – 3=?
A. (y - 1) (y + 3)

B. (y + 1) (y - 3)

C. (y - 1) (y - 3)

D. (y + 2) (y - 3)


Answer:

y2 + 2y – 3


Factorizing the equation and taking y and – 1 as common,


= y2 + 3y – y – 3


= y(y + 3) – 1(y + 3)


= (y + 3)(y – 1).


Question 16.

40 + 3x – x2=?
A. (5 + x) (x - 8)

B. (5 - x) (8 + x)

C. (5 + x) (8 - x)

D. (5 - x) (8 - x)


Answer:

40 + 3x – x2


Factorizing the equation and taking 8 and – x as common,


= 40 + 8x – 3x – x2


= 8(5 + x) – x(5 + x)


= (8 – x)(5 + x).


Question 17.

2x2 + 5x + 3=?
A. (x + 3) (2x + 1)

B. (x + 1) (2x + 3)

C. (2x + 5) (x - 3)

D. none of these


Answer:

2x2 + 5x + 3


Factorizing the equation and taking 2x and 3 as common,


= 2x2 + 2x + 3x + 3


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


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


Question 18.

6a2 – 13a + 6=?
A. (2a + 3) (3a – 2)

B. (2a - 3) (3a + 2)

C. (3a - 2) (2a – 3)

D. (3a + 1) (2a – 3)


Answer:

6a2 – 13a + 6


Factorizing the equation and taking 3a and – 2 as common,


= 6a2 – 9a – 4a+ 6


= 3a(2a – 3) – 2(2a – 3)


= (3a – 2)(2a – 3).


Question 19.

4z2 – 8z + 3=?
A. (2z – 1) (2z – 3)

B. (2z + 1) (3 – 2z)

C. (2z + 3) (3z + 1)

D. (z – 1) (4z – 3)


Answer:

4z2 – 8z + 3


Factorizing the equation and taking 2z and – 1 as common,


= 4z2 – 6z – 2z + 3


= 2z(2z – 3) – 1(2z – 3)


= (2z – 1)(2z – 3).


Question 20.

3 + 23y – 8y2=?
A. (1 - 8y) (3 + y)

B. (1 + 8y) (3 - y)

C. (1 - 8y) (y - 3)

D. (8y - 1) (y + 3)


Answer:

3 + 23y – 8y2


Factorizing the equation and taking 3 and – y as common,


= 3 + 24y – y – 8y2


= 3(1 + 8y) – y(1 + 8y)


= (3 – y)(1 + 8y).