Question

37. Using identity find the product :
(a) (x+3)(x+7) -
(b) (2a - 7) ( 2a-7)
(C) 712
(d) 992
(e) 9982​

Answer 1

Answer:

Step-by-step explanation:

(a) (x +3) (x+7)

Identity : ( a + b ) (a + c) = a^2 + ac + ab + bc

=(x +3) (x +7) = x × x + x × 7 + 3 × x + 3 × 7

= x ^2 +7x +3x + 21 =x^2 + 10x + 21

(b) (2a - 7)(2a -7)

Identity : (a -b ) (a -b ) = (a - b )^2 = a^2 + b^2 -2ab

= (2a -7) (2a - 7) = (2a -7)^2

= (2a )^2 + (7)^2 - 2 × 2a × 7

= 4a^2 + 49 - 28a

= 4a^2 - 28a + 49

(c ) 712

Identity : (a +b )^2 = a^2 + b^2 + 2ab

= 712 = (700 +12 )^2

= (700)^2 + (12)^2 + 2 × 700 × 12

= 490000 + 144 + 16800

= 506944

(d) 992

Identity : (a -b )^2 = a^2 + b^2 - 2ab

= 992 = (1000 - 8)^2

= (1000)^2 + (8)^2 - 2× 1000 × 8

= 1000000 + 64 + 16000

= 1016064