http://s164.photobucket.com/albums/u4/ming21ki/?action=view¤t=P8080048.jpg
http://s164.photobucket.com/albums/u4/ming21ki/?action=view¤t=P8080046.jpg
第２張圖
第一個圈圈，點先變到第２個圈圈
數學歸立法=3= @*@ ../口\ (（＿)(＿）)
2007-08-09 6:53 am
回答 (2)
2007-08-10 10:22 pm
✔ 最佳答案
S(n) = n(a1 +an)/2Since an = a1 + (n - 1)d,
S(n) = n [ a1 + a1 + (n - 1)d ] / 2
S(n) = n[2a1 + (n - 1)d ] / 2
S(n) = n(2a1) / 2 + n [(n - 1)d ] / 2
S(n) = na1 + n(n - 1)d /2
2007-08-09 7:21 am
Where is your picture? I can' t see it.
收錄日期: 2021-04-13 01:00:23
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070808000051KK06522