问题 填空题
化简:(x+y)
x2
x2-y2
+
y2
y-x
=______.
答案

(x+y)

x2
x2-y2
+
y2
y-x

=(x+y)

x2
(x+y)(x-y)
+
y2
y-x

=

x2
x-y
-
y2
x-y

=x+y.

故答案为x+y.

单项选择题
单项选择题