化简(x-yx2-2xy+y2-xy+y2x2-y2)•xyy-1= ___ .

问题描述:

化简(

x-y
x2-2xy+y2
-
xy+y2
x2-y2
)•
xy
y-1
= ___ .

原式=[

x-y
(x-y)2
-
y(x+y)
(x+y)(x-y)
]•
xy
y-1

=(
1
x-y
-
y
x-y
)•
xy
y-1

=
1-y
x-y
xy
y-1

=-
xy
x-y

故答案是:-
xy
x-y

答案解析:首先对括号内的每个分式进行化简,然后进行分式的加减,最后进行乘法运算即可.
考试点:分式的混合运算.
知识点:本题主要考查分式的混合运算,通分、因式分解和约分是解答的关键.