题目内容
先化简再求值:
÷(a+
)(已知a=2+
,b=-1).
| a2-b2 |
| a2-ab |
| 2ab+b2 |
| a |
| 2 |
原式=
÷
=
•
=
,
当a=2+
,b=-1时,原式=
=
=
-1.
| (a+b)(a-b) |
| a(a-b) |
| a2+2ab+b2 |
| a |
=
| a+b |
| a |
| a |
| (a+b)2 |
=
| 1 |
| a+b |
当a=2+
| 2 |
| 1 | ||
2+
|
| 1 | ||
|
| 2 |
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