Question

simplify using identities: (3x +7 )2. (ii) (2a – 5b)2 (iii)3x + 4y) (3x – 4y) ​

Answer 1

Step-by-step explanation:

(I) (3x+7)²

=(3x)²+2×3x×7+(7)²

=9x²+42x+49

(II) (2a-5b)²

=(2a)²-2×2a×5b+(5b)²

=4a²-20ab+25b²

(III) (3x+y)(3x-y)

=(3x²-y²)

Answer 2

Answer:

(i) (3x+7)2 = 2*3x+2*7

=6x+14

(ii) (2a-5b)2 =2*2a-2*5b

=4a-10b

(iii) 3x+4y(3x-4y) = 3x(3x-4y)+4y(3x-4y)

=9x square-12xy+12xy-16y square

Now,

Cancel -12xy+12xy

Answer= 9x square-16y square