等差数列An,Sn=na1+[n(n-1)]*d/2,类比等比数列Bn

问题描述:

等差数列An,Sn=na1+[n(n-1)]*d/2,类比等比数列Bn


无法类比
等比数列的前n项和
(1)q=1, Sn=na1
(2) q≠1 Sn=a1(1-q^n)/(1-q)

Tn=(a1)^n*q^(1+n-1)n/2
Tn为Bn前n项积.