2(x+y)(x-y)-(x+y)^2-(x-y)^2的完全平方公式是?

问题描述:

2(x+y)(x-y)-(x+y)^2-(x-y)^2的完全平方公式是?

=-[(x+y)²-2(x+y)(x-y)+(x-y)²]
=-[(x+y)-(x-y)]²
=(2y)²
=4y²