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