题干
化简
•
．
| 1 |
| a |
| 2 |
| − |
| a |
| a |
| − |
| 1 |
| a |
答案(点此获取答案解析）
解：原式=
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| 1 |
| a |
| 2 |
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| − |
| 1 |
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