问题 解答题
2y+x
x2-y2
+
y
y2-x2
-
2x
x2-y2
答案

原式=

2y+x
x2-y2
-
y
x2-y2
-
2x
x2-y2
=
2y+x-y-2x
x2-y2
=
y-x
(x+y)(x-y)
=-
1
x+y

名词解释
问答题 简答题