1^2 + 2^2 + 3^2 + ... + n^2 點解 = 1/6 n (n+1) (n+2)
要step
收錄日期: 2021-04-13 13:25:44
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070910000051KK05182