题干
先化简，再求值：（
﹣
）÷
，其中a= 3 +1 ．
| a |
| + |
| 1 |
| a |
| 2 |
| a |
| a |
| 1 |
| a |
| 2 |
| 2 |
| a |
| + |
| 1 |
| a |
| 1 |
| a |
答案(点此获取答案解析）
解：原式=
| a |
| + |
| 1 |
| a |
| ( |
| a |
| − |
| 1 |
| ) |
