题目内容
(2011•淮安二模)先化简,再求值:
÷(x+
),其中x=2.
| x |
| x-1 |
| 2x |
| x-1 |
分析:先把括号内通分得到原式=
÷
,再把除法运算转化为乘法运算,然后把分母分解因式得到原式=
•
,再进行约分得原式=
,然后把x=2代入计算即可.
| x |
| x-1 |
| x2-x+2x |
| x-1 |
| x |
| x-1 |
| x-1 |
| x(x+1) |
| 1 |
| x+1 |
解答:解:原式=
÷
=
•
=
,
当x=2时,原式=
=
.
| x |
| x-1 |
| x2-x+2x |
| x-1 |
=
| x |
| x-1 |
| x-1 |
| x(x+1) |
=
| 1 |
| x+1 |
当x=2时,原式=
| 1 |
| 2+1 |
| 1 |
| 3 |
点评:本题考查了分式的化简求值:先把各分式的分子或分母分解因式,若有括号,先把括号内通分,然后约分,得到最简分式或整式,再把满足条件的字母的值代入计算得到对应的分式的值.
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