化简 (x减y)(x加y)加(x减y)加(x加y)等于

问题描述:

化简 (x减y)(x加y)加(x减y)加(x加y)等于

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