(1/x-y-1/x+y)*x²-2xy+y²/(y+1)²-(y-1)²
问题描述：
(1/x-y-1/x+y)*x²-2xy+y²/(y+1)²-(y-1)²
答
原式=(x+y+x-y)/(x+y)(x-y)*(x-y)²/(y+1+y-1)(y+1-y+1)
=2x/(x+y)(x-y)*(x-y)²/4y
=(x²-xy)/(2xy+2y²)