(x+y)^2-8(x^2-y^2)-16(x-y)^2

问题描述:

(x+y)^2-8(x^2-y^2)-16(x-y)^2

错了,是(x+y)^2-8(x^2-y^2)+16(x-y)^2
=[(x+y)-4(x-y)]^2
=(5y-3x)^2