题干
观察下列等式：
=1−
=
，
+
=1−
=
，
+
+
=1−
=
，…则
+
+
+⋯+
=____．（直接填结果，用含n的代数式表示，n是正整数，且n≥1）
| 1 |
| 2 |
| 1 |
| 2 |
| 1 |
| 2 |
| 1 |
| 2 |
| 1 |
| 4 |
| 1 |
| 4 |
| 3 |
| 4 |
| 1 |
| 2 |
| 1 |
| 4 |
| 1 |
| 8 |
| 1 |
| 8 |
| 7 |
| 8 |
| 1 |
| 2 |
| 1 |
| 4 |
| 1 |
| 8 |
| 1 |
| 2 |
| n |
答案(点此获取答案解析）
| 2 |
| n |
| − |
| 1 |
| 2 |
| n |
