问题 解答题
(1)计算:(
2
-1
0+︳1-
2
︳-(
2
-1
2007
2
+1
2008-(-1)-3
(2)先化简,再求值  (1-
x-3
x+3
)÷
2x
x2-9
其中x=4.
答案

(1)原式=1+

2
-1-(
2
+1)×1-(-1),

=1+

2
-1-
2
-1+1,

=0.

(2)原式=[

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

=

6
x+3
×
(x+3)(x-3)
2x

=

3(x-3)
x

当x=4时,

原式=

3×(4-3)
4

=

3
4

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