题干
计算
| b |
| 5 |
| b |
| a |
| 2 |
答案(点此获取答案解析）
解：原式=
×20
| b |
| 5 |
| a |
| 2 |
| b |
=
| b |
| 5 |
| b |
| a |
| 2 |
| b |
| 5 |
| a |
| 2 |
| b |
