Question

化简：（

x-y

x2-2xy+y2

-

xy+y2

x2-y2

）•

xy

y-1

．

Answer 1

（

x-y

x2-2xy+y2

-

xy+y2

x2-y2

）•

xy

y-1

．
=(

1

x-y

-

y

x-y

)•

xy

y-1

，
=-

xy

x-y

．