Maths 公式與代入法
2015-05-09 11:41 pm
回答 (2)
2015-05-10 12:08 am
✔ 最佳答案
28.已知 1² + 2² + ... + n² = n(n + 1)(2n + 1)/6
代 n = 20 可得
1² + 2² + ... + 20²
= 20(20 + 1)(2 × 20 + 1)/6
= 20(21)(41)/6
= 10(7)(41)
= 70(41)
= 2870
2015-05-10 3:33 am
1^2 + 2^2 + ... + 20^2
=20(20+1)(2*20+1)/6
=2870
=20(20+1)(2*20+1)/6
=2870
收錄日期: 2021-04-15 20:07:51
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20150509000051KK00037