Question

Factorise (9a-b)²-49(c-d)²

Answer 1

#BAL

We can write it as

(9a-b)^2 - {7(c-d)}^2

Now put a^2-b^2=(a+b)(a-b)

=>( 9a-b+7c-7d)(9a-b-7c+7d)