计算(x-y)²（x+y）²
问题描述：
计算(x-y)²（x+y）²
答
=[(x-y)(x+y)]^2=(x^2-y^2)^2=x^4-2x^2y^2+y^4
答
(x-y)²(x+y)²
=[(x-y)(x+y)]²
=(x²-y²)²
=x⁴-2x²y²+y⁴