问题 解答题
化简:(
x-y
x2-2xy+y2
-
xy+y2
x2-y2
)•
xy
y-1
答案

x-y
x2-2xy+y2
-
xy+y2
x2-y2
)•
xy
y-1

=(

1
x-y
-
y
x-y
)
xy
y-1

=-

xy
x-y

单项选择题
单项选择题