题干
用数学归纳法证明：1-
+
-
+...+
-
=
+
+...+
第一步应验证的等式是____．
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 4 |
| 1 |
| 2 |
| n |
| - |
| 1 |
| 1 |
| 2 |
| n |
| 1 |
| n |
| + |
| 1 |
| 1 |
| n |
| + |
| 2 |
| 1 |
| 2 |
| n |
答案(点此获取答案解析）
1 -
=
| 1 |
| 2 |
| 1 |
| 2 |
