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