题干
观察等式：①
=1﹣
；②
=
﹣
；③
=
﹣
；④
=
﹣
，…
| 1 |
| 1 |
| × |
| 2 |
| 1 |
| 2 |
| 1 |
| 2 |
| × |
| 3 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 3 |
| × |
| 4 |
| 1 |
| 3 |
| 1 |
| 4 |
| 1 |
| 4 |
| × |
| 5 |
| 1 |
| 4 |
| 1 |
| 5 |
