(x-y+2)(x+y-2)化简.
问题描述：
(x-y+2)(x+y-2)化简.
答
(x-y+2)(x+y-2)
=[x-(y-2)][x+(y-2)]
=x²-2x(y-2)+(y-2)²
=x²-2xy+4x+y²-4y+4