问题 解答题
计算:
(1)
a
a+1
+
a-1
a2-1

(2)
x-y
x+3y
÷
x2-y2
x2+6xy+9y2
-
2y
x+y
答案

(1)原式=

a(a-1)
a2-1
+
a-1
a2-1

=

a2-a+a-1
a2-1

=

a2-1
a2-1

=1;

(2)原式=

x-y
x+3y
(x+3y)2
(x+y)(x-y)
-
2y
x+y

=

x+3y
x+y
-
2y
x+y

=

x+y
x+y

=1.

单项选择题
单项选择题