题目内容
(2013•双峰县模拟)先化简
•
+
,再求值,其中x=
-1.
x2-1 |
x2-2x+1 |
x-1 |
x2+x |
2 |
x |
3 |
分析:首先将分子、分母是多项式的分解因式,进行约分乘法,然后做加法计算,化简以后代入x的数值,即可求解.
解答:解:
•
+
=
•
+
=
+
=
,
当x=
-1时,原式=
=
(
+1).
x2-1 |
x2-2x+1 |
x-1 |
x2+x |
2 |
x |
=
(x+1)(x-1) |
(x-1)2 |
x-1 |
x(x+1) |
2 |
x |
=
x-1 |
x |
2 |
x |
=
x+1 |
x |
当x=
3 |
| ||
|
3 |
2 |
3 |
点评:本题考查了分式的化简求值,正确对分式化简是解题关键.
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