一个无穷等比数列an,前n项和为Sn,lim(趋向于无穷)Sn=6,a1+a2=16/3,则a1=
问题描述:
一个无穷等比数列an,前n项和为Sn,lim(趋向于无穷)Sn=6,a1+a2=16/3,则a1=
答
lim(趋向于无穷)Sn=a1/(1-q)=6,a1+a2=a1+a1*q=16/3
解得a1=4