题干
观察下列各等式：
=
-
，
=
-
，
=
-
，…，根据你发现的规律计算：
+
+
+···+
＝____ (n为正整数)．
| 1 |
| 1 |
| × |
| 2 |
| 1 |
| 1 |
| 1 |
| 2 |
| 1 |
| 2 |
| × |
| 3 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 3 |
| × |
| 4 |
| 1 |
| 3 |
| 1 |
| 4 |
| 2 |
| 1 |
| × |
| 2 |
| 2 |
| 2 |
| × |
| 3 |
| 2 |
| 3 |
| × |
| 4 |
| 2 |
| n |
| ( |
| n |
| + |
| 1 |
| ) |
答案(点此获取答案解析）
| 2 |
| n |
| n |
| + |
| 1 |
