Maths 等差級數
回答 (2)
2009-11-10 5:51 am
✔ 最佳答案
首項 = -28公差 = -20 - (-28) = 8
通項 = -28 + (n - 1)(8)
= 8n - 36
148 = 8n - 36
8n = 184
n = 23
總項數 = 23
23項總和 = 23[2(-28) + (23 - 1)(8)]/2
= 1380
2009-11-10 5:52 am
=4+12+...+ 28 -4-8.....-28+36+44+52....+148
=(148+36) x [ (148-36) / 2 +1 ]
=2200
=(148+36) x [ (148-36) / 2 +1 ]
=2200
參考: me
收錄日期: 2021-04-23 23:23:38
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20091109000051KK01619