(首項+尾項)×項數 / 2
３５，３２，２９．．．．．２
ａ＝３５ ｄ＝３ Ｎ＝？
Ｔ（１）＝３５
Ｔ（Ｎ）＝２
點用式求第幾項？
2006-11-02 4:07 am
回答 (2)
2006-11-03 12:18 am
✔ 最佳答案
First: The equation is wrong. This equation is used to find sum to n term (When first term and the last is known).Used another method:
Ans:
T(n) = a + (n - 1)d
a = 35
d = 32 - 35 = - 3
T(n) = 2
n = ?
2 = 35 + (n - 1)(- 3)
- 33 = - 3n + 3
- 36 = - 3n
3n = 36
n = 12
2006-11-02 4:10 am
３５，３２，２９．．．．．２
ａ＝３５ ｄ＝３ Ｎ＝？
Ｔ（１）＝３５
Ｔ（Ｎ）＝２
N=[(35-2)/3]+1
=33/3+1
=12
ａ＝３５ ｄ＝３ Ｎ＝？
Ｔ（１）＝３５
Ｔ（Ｎ）＝２
N=[(35-2)/3]+1
=33/3+1
=12
收錄日期: 2021-04-23 15:49:01
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20061101000051KK03648