已知数列an满足a1=1 Sn=2an+n 求an

来源：学生作业帮助网编辑：六六作业网时间：2024/12/22 01:55:07

已知数列an满足a1=1Sn=2an+n求an已知数列an满足a1=1Sn=2an+n求an已知数列an满足a1=1Sn=2an+n求ann=1时,a1=S1=2a1+1a1=-1n≥2时,an=Sn

已知数列an满足a1=1 Sn=2an+n 求an
已知数列an满足a1=1 Sn=2an+n 求an

已知数列an满足a1=1 Sn=2an+n 求an
n=1时,a1=S1=2a1+1
a1=-1
n≥2时,an=Sn-S(n-1)=2an+n-[2a(n-1)+(n-1)]
an=2a(n-1)-1
an-1=2a(n-1)-2=2[a(n-1)-1]
(an -1)/[a(n-1)-1]=2,为定值
a1-1=-1-1=-2,数列{an-1}是以-2为首项,2为公比的等比数列
an -1=(-2)·2^(n-1)=-2ⁿ
an=1-2ⁿ
数列{an}的通项公式为an=1-2ⁿ

已知数列{an}满足a1=1/2,sn=n^2an,求通项an 已知数列{an},满足a1=1/2,Sn=n²×an,求an 已知数列an满足a1=1/2 sn=n平方×an 求an 已知数列An满足 A1=1/2 Sn=N²An 求An 已知数列an满足a1=1 Sn=2an+n 求an 已知数列{an}满足:a1=3,an=Sn-1+2n,求数列an及sn 已知数列an满足a1=1 ,Sn=(n+1)*an/2,求通项的表达式. 已知数列{an}中a1=1,且满足an+an-1不等于0,Sn=1/6*(an+1)(an+2).(1)求通项an,并说明{an}是什么数列(2)求数列{an}的前n项和Sn 已知数列an的前n项和sn与通项an满足a1=2,sn+1sn=an+1,求sn 已知数列{an}a1=2前n项和为Sn 且满足Sn Sn-1=3an 求数列{an}的通项公式an已知数列{an}a1=2前n项和为Sn 且满足Sn +Sn-1=3an 求数列{an}的通项公式an 已知数列{an}满足a1=1,Sn=[(n+1)/2]*an,求通项an.急,思路也要已知数列｛an｝满足an+1+an=4n-3 当a1=2时,求Sn 已知数列{an}满足a1=1,an+1=2an+1.(1)求证:数列{an+1}是等比数列;(2)求an和Sn的表达式. 数列an满足a1=1/3,Sn=n(2n-1)an,求an 已知数列an中,a1=1,前项n和sn与通项an满足an=2sn2/2sn-1,求通项的an表达式已知sn为数列an的前n项和,其中满足a1=4,an=3an-1-2,求an及sn 已知正数数列an满足a1=1 sn=1/2（an+1/an),其中sn为其前n项和,则sn=?请详解已知数列An的前n项和Sn满足An+2Sn*Sn-1=0,n大于等于2,A1=1/2,求An.