（xy-x^2)乘以(xy)/(x-y)=x(y-x)乘以（xy）/(x-y)=-x(x-y)乘以（xy）/(x-y)=-x^2y这样做对吗?

Question

（xy-x^2)乘以(xy)/(x-y)
= x(y-x)乘以（xy）/(x-y)
= -x(x-y)乘以（xy）/(x-y)
= -x^2y
这样做对吗?

Answer 1

对 .
前提是x不等于y