题目内容
先化简，再求值：（
-2）÷
，其中x=
-4．
| x |
| x-2 |
| x2-16 |
| x2-2x |
| 3 |
原式=（
-
）÷
=
÷
=
•
=
•
=-
，
当x=
-4时，原式=-
=-
=
．
| x |
| x-2 |
| 2(x-2) |
| x-2 |
| x2-16 |
| x2-2x |
=
| x-2x+4 |
| x-2 |
| x2-42 |
| x2-2x |
=
| -x+4 |
| x-2 |
| x(x-2) |
| (x+4)(x-4) |
=
| -(x-4) |
| x-2 |
| x(x-2) |
| (x+4)(x-4) |
=-
| x |
| x+4 |
当x=
| 3 |
| x |
| x+4 |
| ||
|
4
| ||
| 3 |
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