题目内容
(1+
)+(1+
×2)+(1+
×3)+…+(1+
×15).
| 19 |
| 92 |
| 19 |
| 92 |
| 19 |
| 92 |
| 19 |
| 92 |
(1+
)+(1+
×2)+(1+
×3)+…+(1+
×15),
=15+
×(1+2+3+…+15),
=15+
×120,
=39
.
| 19 |
| 92 |
| 19 |
| 92 |
| 19 |
| 92 |
| 19 |
| 92 |
=15+
| 19 |
| 92 |
=15+
| 19 |
| 92 |
=39
| 18 |
| 23 |
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