已知等差数列{an}的前n项和为Sn,a1=2,且Sn=λnan+1(λ为常数且λ不等于1) .(1) 求λ的值;(2) 若bn=(1/2) ∧an,求数列{bn} 的前n项和Tn

问题描述:

已知等差数列{an}的前n项和为Sn,a1=2,且Sn=λnan+1(λ为常数且λ不等于1) .(1) 求λ的值;(2) 若bn=(1/2) ∧an,求数列{bn} 的前n项和Tn

(1)令n=1,则有S1=λa1+1即2=2λ+1得λ=1/2
(2)bn/bn+1=(1/2)∧d,{bn}为等比数列