Question

(x + 2y) - 4(2x - y)2​

Answer 1

Answer:

First one uses the result that:

a2−b2=(a−b)(a+b)

In this case we have:

a=x+2y,b=2(2x−y)=4x−2y

So we get:

(x+2y)2−(2(2x−y))2=(x+2y−(4x−2y))(x+2y+4x−2y) or:

(−3x+4y)(5x)

In this case use the factorisation which is already given.

This saves a lot of work.