感激不尽啊!数列t1,t2,t3,...,tn,中,t1=23,n>1时,tn=tn-1-3,当n为何值得时候是的tn=-4?

分类: 作业答案 • 2021-12-19 10:48:15

问题描述：

感激不尽啊!
数列t1,t2,t3,...,tn,中,t1=23,n>1时,tn=tn-1-3,当n为何值得时候是的tn=-4?

答

tn = 26-3n
tn =-4
26-3n=-4
3n=30
n=10

答

tn=t(n-1)-3
tn-t(n-1) =-3
tn - t1 = -3(n-1)
tn = 26-3n
tn =-4
26-3n=-4
3n=30
n=10