题目内容
已知x=
，求
-
=
| 1 | ||
2+
|
| x2-2x+1 |
| x-1 |
| ||
| x2-x |
-1-2
| 3 |
-1-2
．| 3 |
分析：由已知可求得
，再把原式化简代入即可．
| 1 |
| x |
解答：解：∵x=
=2-
＞0，∴
=2+
，
∴
-
=
-
=x-1-
=2-
-1-(2+
)=-1-2
．
故答案为-1-2
．
| 1 | ||
2+
|
| 3 |
| 1 |
| x |
| 3 |
∴
| x2-2x+1 |
| x-1 |
| ||
| x2-x |
| (x-1)2 |
| x-1 |
| x-1 |
| x(x-1) |
| 1 |
| x |
| 3 |
| 3 |
| 3 |
故答案为-1-2
| 3 |
点评：正确化简和计算是解题的关键．
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