【xy-x²】*xy/x-y
问题描述：
【xy-x²】*xy/x-y
答
解
(xy-x²)xy/(x-y)
=x²y(y-x)/[-(y-x)]
=-x²y
【xy-x²】*xy/x-y
解
(xy-x²)xy/(x-y)
=x²y(y-x)/[-(y-x)]
=-x²y