计算：x-y2x+2y-x2+y2x2-y2．

题型：解答题难度：一般来源：不详

计算：

x-y

2x+2y

-

x2+y2

x2-y2

．

答案

原式=

x-y

2(x+y)

-

x2+y2

(x+y)(x-y)

=

(x-y)(x-y)

2(x+y)(x-y)

-

2(x2+y2)

2(x+y)(x-y)

=

x2-2xy+ y2-2x2-2y2

2(x+y)(x-y)

=-

x+y

2(x-y)

．