Question

Identify the factors of x^2 + 49y^2.

(x + 7y)(x + 7y)

Prime

(x - 7y)(x - 7y)

(x + 7y)(x - 7y)

Answer 1

what's 2nd option?

Answer 2

that its prime

Answer 3

yup, it's prime

Answer 4

because (x+7y)(x+7y)=(x+7y)^2=x^2+49y^2+14xy
which is not equal to x^2+49y^2
(x-7y)(x-7y)=(x-7y)^2=x^2+49y^2-14xy

(x-7y)(x+7y)=x^2-(7y)^2=x^2-49y^2 because
\[a ^{2}-b ^{2}=(a+b)(a-b)\]