Question

因式分解：(x-y)方-4(x方-y方）+4(x+y)方

Answer 1

(x+y)^2-4(x^2-y^2)+4(x-y)^2

=(x+y)^2-2*2(x+y)(x-y)+4(x-y)^2

=[(x+y)-2(x-y)]^2

=(3y-x)^2