(x2-y2)2 1 1 ((x-y)(x+y))2 y2-x2 (x-y)2(x+y)2 (x+y)(x-y) (x-y)2 * x2y2
-------------- : (---- - ----) = --------------- : (---------) = ---------------- : (- --------------) = - ------------------ =
x2+2xy+y2 x2 y2 (x+y)2 x2y2 (x+y)2 x2y2 (x+y)(x-y)
x2y2(x-y)
=- -------------
x+y