Question

（2012•黄冈二模）化简(

x-y

x2-2xy+y2

-

xy+y2

x2-y2

)•

xy

y-1

=

-

xy

x-y

．

Answer 1

分析：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．

解答：解：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

．

点评：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．