請比埋計左條式我thx
In the arithmetic progression 97, 93, 89, 85, …, find
the first term a of the arithmetic progression;
the common difference d of the arithmetic progression
the general term T(n) of the arithmetic progression
the first negative term of the arithmetic progression (i.e. the smallest n such that T(n) < 0)
唔識做呢條數....20分...好急
2006-12-18 3:26 am
回答 (2)
2006-12-18 4:02 am
✔ 最佳答案
the first term is 97the common difference d =93-97=89-93= -4
***(general term
= the first term + ( term-1 )* the common difference = a+(n-1)*d )***
the general term T(n)
=a+(n-1)*d
=97+(n-1)*-4
=97-4(n-1)
let the first negative term =T(y)
T(y)<0
97-4(y-1)<0
97<4y-4
101<4y
y>25.25
therefore,
the first negative term =T(26), as n must be a integer
T(26)=97-4(26-1)=-3
so, the first negative term=T(26)= -3
參考: 自己
2006-12-18 3:33 am
first term is 97
common difference d is -4
T(n) = a + nd = 97+(-4)n = 97-4n
T(n)<0
97-4n<0
4n>97
n>97/4
So n=100
common difference d is -4
T(n) = a + nd = 97+(-4)n = 97-4n
T(n)<0
97-4n<0
4n>97
n>97/4
So n=100
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原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20061217000051KK04162