题干
先化简：（a+1﹣
）÷
，再任选一个你喜欢的数a代入求值．
| 3 |
| a |
| 1 |
| a |
| a |
| 1 |
| a |
| 3 |
| a |
| 1 |
| a |
| a |
| 1 |
| a |
