(1)a1=20,an=54,n项和为999,求d和n(2)d=1/3,n=37,n项和为629,求a1和an(3)a1=5/6,d=-1/6,n项和为-5,求n和an(4)d=2,n=15,an=-10,求a1和n项和

(1)a1=20,an=54,n项和为999,求d和n(2)d=1/3,n=37,n项和为629,求a1和an(3)a1=5/6,d=-1/6,n项和为-5,求n和an(4)d=2,n=15,an=-10,求a1和n项和 Sn=2an+n a1=1 求an其中{an}的前N项和为Sn 设数列｛an｝前n项和为sn,sn=a1(3^n-1)／2(n>=1),且a4=54,则a1= 设数列{an}的前n项和为sn,sn=a1(3^n-2)/2(n≥1),a4=54,则a1= An=2An-1+2^n+2,n》2,A1=2,Sn为数列{An}的前N项和,证明Sn>n^3+n^2 已知数列{an}满足3an+1+an=4,a1=9,前n项和为sn,则满足不等式/sn-n-6/ 已知数列{an}满足3an+1+an=4,a1=9,前n项和为sn,则满足不等式/sn-n-6/ 已知数列{an}满足3an+1+an=4,a1=9,前n项和为sn,则满足不等式/sn-n-6/ 设数列an的前n项和为Sn,Sn=a1(3^n-1)/2,且a4=54,则a1为? 在数列{An}中,A1=2 An+1=4An-3n+1 n为正整数 求{An}的前n项和Sn 设等比数列{an}的前n项和为Sn,已知a1=2011,且an+2an+1+an+2=0(N∈N*),则S2012? 设数列{an}的前n项和为Sn,a1=10,a(n+1)=9Sn+10 已知Sn为等差数列{an}的前n项和,Sn=12n-n².（1）|a1|+|a2|+|a3|+...+|a10|;（2）求|a1|+|a2|+...+|an| 数列{an}中前n项和为sn且a1=2,snsn-1=an,求an a1=9,3a(n+1)+an=4.Sn为an前n项和,求|Sn-n-6| 已知数列{an}的前n项和为Sn,若a1=1/2,Sn=n^2an-n(n-1)求Sn,an 已知数列{an}的前n项和为Sn,a1=1/2,且Sn=n^2An-n(n-1),求an 数列2^n*An 的前n项和为Sn=9-6n求An通项公式:我a1=3/2Sn=((a1+an)*n/2)*2^n求an,错在?