Question

Q.1. Use suitable identities to find the
following products :
(i) (x + 4) (x + 10)
(ii) (x + 8) (x - 10)
(iii) (3x + 4) (3x - 5)
در
(iv)
2
(v) (3 - 2x) (3 + 2x)​

Answer 1

Answer:

(i) (x + 4) (x + 10) Suitable identity is (x + a) (x + b) = x2 + (a + b)x + ab (x + 4) (x + 10) = x2 + (4 + 10)x + (4 × 10) = x2 + 14x + 40

(ii) (x + 8) (x- 10) Suitable identity is (x + a) (x + b) = x2 + (a + b)x + ab (x + 8) (x – 10) = (x)2 + (8 – 10)x + (8 × -10) = x2 + (-2)x + (-80) = x2 – 2x – 80

(iii) (3x + 4) (3x – 5) Suitable identity is (x + a) (x + b) = x2 + (a + b)x + ab (3x + 4) (3x – 5) = (3x)2 + (+4 – 5)3x + (4 x -5) = 9x2 + (-1)3x + (-20) = 9x2 – 3x – 20

(iv)Suitable identity is (a + b) (a – b) = a2 – b2 (v) (3 – 2x) (3 + 2x) Suitable identity is (a + b) (a – b) = a2 – b2 (3 – 2x) (3 + 2x) = (3)2 – (2x)2 = 9 – 4x2 .

Answer 2

Answer:

(i) (x+4) (x+10)

Using (x+a)(x+b) = x^2 + x(a + b ) + ab

= x^2+ 14x+ 40

(ii) (x+8) ( x-10)

Using (x+a)( x-b) = x^2 - x(a+b) -ab

= x^2-2x-80

(iiii) (3x+4)(3x-5)

Using (x+a) (x-b) = x^2 - x(a+b) -ab

= 9x^2 - 3x-20