问题 解答题
计算.
 (1)
x
x-3
-
x
x+3

(2)
1
m+2
+
4
m2-4
答案

(1)

x
x-3
-
x
x+3

=

x(x+3)
(x-3)(x+3)
-
x(x-3)
(x-3)(x+3)

=

6x
x2-9

(2)

1
m+2
+
4
m2-4

=

m-2
(m+2)(m-2)
+
4
(m+2)(m-2)

=

1
m-2

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