题干
观察下列各式：
=
﹣
；
=
−
；
=
−
；
=
﹣
；…．
| 1 |
| 1 |
| 2 |
| 1 |
| 1 |
| 1 |
| 2 |
| 1 |
| 2 |
| 3 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 3 |
| 4 |
| 1 |
| 3 |
| 1 |
| 4 |
| 1 |
| 4 |
| 5 |
| 1 |
| 4 |
| 1 |
| 5 |
.
