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Factors Of Polynomials

Class 8th Mathematics (old) MHB Solution
Exercise 85
  1. x^2 + 2x - 63 Find the factors.
  2. y^2 + 7y - 44 Find the factors.
  3. x^2 + 3x - 40 Find the factors.
  4. k^2 - 2k - 120 Find the factors.
  5. p^2 - p - 420 Find the factors.
  6. x^2 + 25x + 144 Find the factors.
  7. x^2 - 10x - 144 Find the factors.
  8. x^2 + 27x + 72 Find the factors.
  9. x^2 - 36x + 203 Find the factors.
  10. y^2 - 6y - 72 Find the factors.
  11. p^2 + 27x - 90 Find the factors.
  12. x^2 - 36x + 324 Find the factors.
  13. y^2 + 6y - 135 Find the factors.
  14. s^2 - 2s - 399 Find the factors.
  15. x^2 + 36x + 35 Find the factors.
  16. 11x^2 - 18x + 7 Find the factors.
  17. 4p^2 - 9p - 9 Find the factors.
  18. 6x^2 - 25xy - 9y^2 Find the factors.
  19. 5x^2 + 21xy - 20y^2 Find the factors.
  20. 3p^2 - 14p + 15 Find the factors.
  21. 6m^2 - m - 12 Find the factors.
  22. 7x^2 - 5xy - 18y^2 Find the factors.
  23. 9x^2 + 5xy - 14y^2 Find the factors.
  24. 4m^2 + 19mm + 12n^2 Find the factors.
  25. 7p^2 + 18pq - 9p^2 Find the factors.
  26. 3x^2 + 3x - 1260 Find the factors.
  27. 5y^2 - 30y - 360 Find the factors.
  28. 3x^2 + 3x - 1260y^2 Find the factors.
  29. 5y^2 z^2 - 5yz - 360 Find the factors.
Exercise 86
  1. 27m^3 + 125n^3 Use the formula to find the factors.
  2. p^3 + 64q^3 Use the formula to find the factors.
  3. y^3 + 216 Use the formula to find the factors.
  4. 2a^3 + 250b^3 Use the formula to find the factors.
  5. 343 + 512k^3 Use the formula to find the factors.
  6. a^3 + 1/8a^3 Use the formula to find the factors.
Exercise 87
  1. x^3 - 8y^3 Use the formula to find the factors.
  2. 125m^3 - 27n^3 Use the formula to find the factors.
  3. 64a^3 - 1 Use the formula to find the factors.
  4. (x + y)^3 - 125 Use the formula to find the factors.
  5. 216 - 27q^3 Use the formula to find the factors.
  6. 512x^3 - 343y^3 Use the formula to find the factors.
  7. 729b^3 - 64 Use the formula to find the factors.
  8. x^3 - 1/x^3 Use the formula to find the factors.
  9. 8y^3 - 27/y^3 Use the formula to find the factors.

Exercise 85
Question 1.

Find the factors.

x2 + 2x – 63


Answer:

x2 + 2x – 63

⟹ x2 + 9x – 7x – 63


⟹ x(x + 9) – 7(x + 9)


⟹ (x – 7) (x + 9)


So (x – 7) and (x + 9) are the factors of the given polynomial.



Question 2.

Find the factors.

y2 + 7y – 44


Answer:

y2 + 7y – 44

⟹ y2 + 11y – 4y – 44


⟹ y(y + 11) – 4(y + 11)


⟹ (y – 4) (y + 11)


So (y – 4) and (y + 11) are the factors of the given polynomial.



Question 3.

Find the factors.

x2 + 3x – 40


Answer:

x2 + 3x – 40

⟹ x2 + 8x – 5x – 40


⟹ x(x + 8) – 5(x + 8)


⟹ (x – 5) (x + 8)


So (x – 5) and (x + 8) are the factors of the given polynomial.



Question 4.

Find the factors.

k2 – 2k – 120


Answer:

k2 – 2k – 120

⟹ k2 + 10k – 12k – 120


⟹ k(k + 10) – 12(k + 10)


⟹ (k – 12) (k + 10)


So (k – 12) and (k + 10) are the factors of the given polynomial.



Question 5.

Find the factors.

p2 – p – 420


Answer:

p2 – p – 420

⟹ p2 + 20p – 21p – 420


⟹ p(p + 20) – 21(p + 20)


⟹ (p – 21) (p + 20)


So (p – 21) and (p + 20) are the factors of the given polynomial.



Question 6.

Find the factors.

x2 + 25x + 144


Answer:

x2 + 25x + 144

⟹ x2 + 9x + 16x + 144


⟹ x(x + 9) + 16(x + 9)


⟹ (x + 16) (x + 9)


So (x + 16) and (x + 9) are the factors of the given polynomial.



Question 7.

Find the factors.

x2 – 10x – 144


Answer:

x2 – 10x – 144

⟹ x2 + 8x – 18x – 144


⟹ x(x + 8) – 18(x + 144)


⟹ (x – 18) (x + 8)


So (x – 18) and (x + 8) are the factors of the given polynomial.



Question 8.

Find the factors.

x2 + 27x + 72


Answer:

x2 + 27x + 72

⟹ x2 + 3x + 24x + 72


⟹ x(x + 3) + 24(x + 3)


⟹ (x + 3) (x + 24)


So (x + 3) and (x + 24) are the factors of the given polynomial.



Question 9.

Find the factors.

x2 – 36x + 203


Answer:

x2 – 36x + 203

⟹ x2 – 29x – 7x – 203


⟹ x(x – 29) – 7(x – 29)


⟹ (x – 7) (x – 29)


So (x – 7) and (x – 29) are the factors of the given polynomial.



Question 10.

Find the factors.

y2 – 6y – 72


Answer:

y2 – 6y – 72

⟹ y2 – 12y + 6y – 72


⟹ y(y – 12) + 6(y – 12)


⟹ (y – 12) (y + 6)


So (y – 12) and (y + 6) are the factors of the given polynomial.



Question 11.

Find the factors.

p2 + 27x – 90


Answer:

p2 + 27x – 90

⟹ p2 + 30p – 3p – 90


⟹ p(p + 30) – 3(p + 30)


⟹ (p – 3) (p + 30)


So (p – 3) and (p + 30) are the factors of the given polynomial.



Question 12.

Find the factors.

x2 – 36x + 324


Answer:

x2 – 36x + 324

⟹ x2 – 18x – 18x – 203


⟹ x(x – 18) – 18(x – 18)


⟹ (x – 18) (x – 18)


So (x – 18) is the factors of the given polynomial.



Question 13.

Find the factors.

y2 + 6y – 135


Answer:

y2 + 6y – 135

⟹ y2 + 15y – 9y – 135


⟹ y(y + 15) – 9(y + 15)


⟹ (y + 15) (y – 9)


So (y – 9) and (y + 15) are the factor of the given polynomial.



Question 14.

Find the factors.

s2 – 2s – 399


Answer:

s2 – 2s – 399

⟹ s2 – 21s + 19s – 399


⟹ s(s – 21) + 19(s – 21)


⟹ (s – 21) (y + 19)


So (s – 21) and (s + 19) are the factors of the given polynomial.



Question 15.

Find the factors.

x2 + 36x + 35


Answer:

x2 + 36x + 35

⟹ x2 + 35x + x + 35


⟹ x(x + 35) + x(x + 35)


⟹ (x + 1) (x + 35)


So (x + 35) and (x + 1) are the factors of the given polynomial.



Question 16.

Find the factors.

11x2 – 18x + 7


Answer:

11x2 – 18x + 7

⟹ 11x2 – 11x – 7x – 7


⟹ 11x(x – 1) – 7(x – 1)


⟹ (11x – 7) (x – 1)


So (11x – 7) and (x – 1) are the factors of the given polynomial.



Question 17.

Find the factors.

4p2 – 9p – 9


Answer:

4p2 – 9p – 9

⟹ 4p2 – 12p + 3p – 9


⟹ 4p(p – 3) + 3(p – 3)


⟹ (p – 3) (4p + 3)


So (p – 3) and (4p + 3) are the factors of the given polynomial.



Question 18.

Find the factors.

6x2 – 25xy – 9y2


Answer:

6x2 – 25xy – 9y2

⟹ 6x2 – 27xy + 2xy – 9y2


⟹ 3x(2x – 9y) – 1y(2x – 9y)


⟹ (2x – 9y) (3x – 1y)


So (2x – 9y) and (3x – 1y) are the factors of the given polynomial.



Question 19.

Find the factors.

5x2 + 21xy – 20y2


Answer:

5x2 + 21xy – 20y2

⟹ 5x2 – 25xy + 4xy – 20y2


⟹ 5x(x – 5y) + 4y(x – 5y)


⟹ (5x + 4y) (x – 5y)


So (5x + 4y) and (x – 5y) are the factors of the given polynomial.



Question 20.

Find the factors.

3p2 – 14p + 15


Answer:

3p2 – 14p + 15

⟹ 3p2 – 9p – 5p + 15


⟹ 3p(p – 3) – 5(p – 3)


⟹ (p – 3) (3p – 5)


So (p – 3) and (3p – 5) are the factors of the given polynomial.



Question 21.

Find the factors.

6m2 – m – 12


Answer:

6m2 – m – 12

⟹ 6m2 – 9m + 8m – 12


⟹ 3m(2m – 3) + 4(2m – 3)


⟹ (3m + 4) (2m – 3)


So (3m + 4) and (2m – 3) are the factors of the given polynomial.



Question 22.

Find the factors.

7x2 – 5xy – 18y2


Answer:

7x2 – 5xy – 18y2

⟹ 7x2 – 14xy + 9xy – 18y2


⟹ 7x(x – 2y) + 9y(x – 2y)


⟹ (7x + 9y) (x – 2y)


So (7x + 9y) and (x – 2y) are the factors of the given polynomial.



Question 23.

Find the factors.

9x2 + 5xy – 14y2


Answer:

9x2 + 5xy – 14y2

⟹ 9x2 – 14xy + 9xy – 14y2


⟹ 9x(x – y) – 14y(x – y)


⟹ (9x – 14y) (x – y)


So (9x – 14y) and (x – y) are the factors of the given polynomial.



Question 24.

Find the factors.

4m2 + 19mm + 12n2


Answer:

4m2 + 19mn + 12 n2

⟹ 4m2 + 16nm + 3mn + 12 n2


⟹ 4m(m + 4n) + 3(m + 4n)


⟹ (4m + 3) (m + 4n)


So (4m + 3) and (m + 4n) are the factors of the given polynomial.



Question 25.

Find the factors.

7p2 + 18pq – 9p2


Answer:

7p2 + 18pq – 9q2

⟹ 7p2 + 21pq – 3pq – 9q2


⟹ 7p(p + 3q) – 3(p + 3q)


⟹ (7p – 3) (p + 3q)


So (7p – 3) and (p + 3q) are the factors of the given polynomial.



Question 26.

Find the factors.

3x2 + 3x – 1260


Answer:

3x2 + 3x – 1260

⟹ 3x2 – 60x + 63x – 1260


⟹ 3x(x – 20) – 63(x – 60)


⟹ (3x – 63) (x – 20)


So (3x – 63) and (x – 20) are the factors of the given polynomial.



Question 27.

Find the factors.

5y2 – 30y – 360


Answer:

5y2 – 30y – 360

⟹ 5y2 – 60y + 30y – 360


⟹ 5y(y – 12) + 30(y – 12)


⟹ (y – 12) (5y + 30)


So (y – 12) and (5y + 30) are the factor of the given polynomial.



Question 28.

Find the factors.

3x2 + 3x – 1260y2


Answer:

3x2 + 3xy – 1260y2

⟹ 3x2 – 60xy + 63xy – 1260 y2


⟹ 3x(x – 20y) – 63y(x – 60y)


⟹ (3x – 63y) (x – 20y)


So (3x – 63y) and (x – 20y) are the factors of the given polynomial.



Question 29.

Find the factors.

5y2z2 – 5yz – 360


Answer:

5y2 z2 – 5yz– 360

⟹ 5y2z2 – 45yz + 40yz – 360


⟹ 5yz(yz – 9) + 40(yz – 9)


⟹ (yz – 9) (5yz + 40)


So (yz – 9) and (5yz + 40) are the factor of the given polynomial.




Exercise 86
Question 1.

Use the formula to find the factors.

27m3 + 125n3


Answer:

27m3 + 125n3

⟹ (3m)3 + (5n)3


Using the formula (a3 + b3) = (a + b) (a2 – ab + b2)


Here a = 3m and b = 5n.


⟹ (3m + 5n) (9m2 – 15mn + 25n2)



Question 2.

Use the formula to find the factors.

p3 + 64q3


Answer:

p3 + 64q3

⟹ (p)3 + (4q)3


Using the formula (a3 + b3) = (a + b) (a2 – ab + b2)


Here a = p and b = 4q.


⟹ (p + 4q) (p2 – 4pq + 16q2)



Question 3.

Use the formula to find the factors.

y3 + 216


Answer:

y3 + 216

⟹ (y)3 + (6)3


Using the formula (a3 + b3) = (a + b)(a2 – ab + b2)


Here a = y and b = 6.


⟹ (y + 6) (y2 – 6y + 36)



Question 4.

Use the formula to find the factors.

2a3 + 250b3


Answer:

2a3 + 250b3

⟹ 2× [a3 + 250b3]


⟹ 2× [(a) 3 + (5b)3]


Using the formula (a3 + b3) = (a + b) (a2 – ab + b2)


Here a = a and b = 5b.


⟹ 2× (a + 5b) (a2 – 5ab + 25b2)


⟹ (2a + 10b) (a2 – 5ab + 25b2)



Question 5.

Use the formula to find the factors.

343 + 512k3


Answer:

512k3 + 343

⟹ (8k)3 + (7)3


Using the formula (a3 + b3) = (a + b) (a2 – ab + b2)


Here a = 8k and b = 7.


⟹ (8k + 7) (64k2 – 56k + 49)



Question 6.

Use the formula to find the factors.



Answer:

a3 + 1/8a3

⟹ (a)3 + (1/2a)3


Using the formula (a3 + b3) = (a + b) (a2 – ab + b2)


Here a = a and b = 1/2a.


⟹ (a + 1/2a)(a2 – 1/2 + 1/4a2)




Exercise 87
Question 1.

Use the formula to find the factors.

x3 – 8y3


Answer:

x3 – 8y3

⟹ (x)3 – (2y)3


Using the formula (a3 + b3) = (a – b) (a2 + ab + b2)


Here a = x and b = 2y.


⟹ (x – 2y) (x2 + 2xy + 4y2)



Question 2.

Use the formula to find the factors.

125m3 – 27n3


Answer:

125m3 – 27n3

⟹ (5m)3 – (3n)3


Using the formula (a3 + b3) = (a – b) (a2 + ab + b2)


Here a = 5m and b = 3n.


⟹ (5m – 3n)(25m2 + 15mn + 9n2)



Question 3.

Use the formula to find the factors.

64a3 – 1


Answer:

64a3 – 1

⟹ (4a)3 – (1)3


Using the formula (a3 + b3) = (a – b) (a2 + ab + b2)


Here a = 4a and b = 1.


⟹ (4a – 1) (16a2 + 4a + 1)



Question 4.

Use the formula to find the factors.

(x + y)3 – 125


Answer:

(x + y)3 – 125

⟹ (x + y)3 – (5)3


Using the formula (a3 + b3) = (a – b) (a2 + ab + b2)


Here a = x + y and b = 5.


⟹ (x + y + 5) ((x + y)2 – 6(x + y) + 36)



Question 5.

Use the formula to find the factors.

216 – 27q3


Answer:

216 – 27q3

⟹ (6)3 – (3q)3


Using the formula (a3 + b3) = (a – b) (a2 + ab + b2)


Here a = 6 and b = 3q.


⟹ (6 – 3q) (36 – 18q + 9q2)



Question 6.

Use the formula to find the factors.

512x3 – 343y3


Answer:

512x3 – 343y3

⟹ (8x)3 – (7y)3


Using the formula (a3 + b3) = (a – b) (a2 + ab + b2)


Here a = 8x and b = 7y.


⟹ (8x – 7y) (64x2 + 56xy + 49y2)



Question 7.

Use the formula to find the factors.

729b3 – 64


Answer:

729b3 – 64

⟹ (9b)3 – (4)3


Using the formula (a3 + b3) = (a – b) (a2 + ab + b2)


Here a = 9b and b = 4.


⟹ (9b – 4) (81b2 + 36b + 16)



Question 8.

Use the formula to find the factors.



Answer:

x3 – 1/x3

⟹ (x)3 – (1/x)3


Using the formula (a3 - b3) = (a – b) (a2 + ab + b2)


Here a = x and b = 1/x.


⟹ (x – 1/x) (x2 + 1 + 1/x2)


Question 9.

Use the formula to find the factors.



Answer:

8y3 – 27/y3

⟹ (2y)3 – (3/y)3


Using the formula (a3 + b3) = (a – b)(a2 + ab + b2)


Here a = 2y and b = 3/y.


⟹ (2y – 3/y)(4y2 – 6 + 9/y2)