问题 填空题
计算:(
x
x-y
+
y
y-x
xy
x-y
=______.
答案

原式=(

x
x-y
-
y
x-y
)•
x-y
xy

=

x-y
x-y
x-y
xy

=

x-y
xy

故答案为

x-y
xy

单项选择题
单项选择题