题目内容
先化简，再求值(
-
)•
，其中x=
．
| 3 |
| x-1 |
| 1 |
| x+1 |
| x2-1 |
| x |
| 2 |
(
-
)•
=
•
=
；
当x=
时，原式=
=2+2
．
| 3 |
| x-1 |
| 1 |
| x+1 |
| x2-1 |
| x |
=
| 3x+3-x+1 |
| x2-1 |
| x2-1 |
| x |
=
| 2x+4 |
| x |
当x=
| 2 |
2
| ||
|
| 2 |
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