题干
计算：
−
．
| a |
| 2 |
| a |
| b |
| b |
| 2 |
| a |
| b |
答案(点此获取答案解析）
解：原式=
= {#mathml#
| a |
| 2 |
| − |
| b |
| 2 |
| a |
| − |
| b |
