题干
用数学归纳法证明：1+
+
+…
=
（n∈N*），由“k递推到k+1”时左端需增加的代数式是____．
| 1 |
| 1 |
| + |
| 2 |
| 1 |
| 1 |
| + |
| 2 |
| + |
| 3 |
| 1 |
| 1 |
| + |
| 2 |
| + |
| 3 |
| + |
| ⋯ |
| + |
| n |
| 2 |
| n |
| n |
| + |
| 1 |
答案(点此获取答案解析）
| 2 |
| ( |
| k |
| + |
| 1 |
| ) |
| ( |
| k |
| + |
| 2 |
| ) |
