等差数列{an}的前n项和为Sn,满足a3=7,且a5+a7=26,求：令bn=1∕(an²-4﹚,求数列bn的前n项和

设数列an的前n项和为Sn,满足an+sn=An^2+Bn+1(A不等于0)an为等差数列,求(B-1)/A (1)已知数列an的前n项和为sn满足sn=an²+bn,求证an是等差数列(2)已知等差数列an的前n项和为sn,求证数列sn/n也成等差数列 求证等差数列!已知数列an的各项均为正数,前n项和为Sn,且满足2Sn=a∧2n+n-4 设等差数列{an}的前n项和为Sn,且满足S15>0,S16 设Sn为等差数列an的前n项和.求证Sn/n为等差数列 等差数列{an}的前n项和为sn,a10 设Sn为等差数列{An}的前n项和,求证：{Sn/n}是等差数列 已知数列{an}的前n项和为Sn,且满足an+2Sn*Sn-1=0,a1=1/2.求证：{1/Sn}是等差数列 已知等差数列{an}的前n项和为Sn,满足关系lg(Sn+1)=n (n∈N*).试证明数列{an}为等比数列 已知等差数列{an}的前n项和Sn满足：Sn=n^2+2n+a (n属于N*）则实数a= 已知等差数列an的前n项和为sn 且满足Sn=n²+n,则通项公式an=? 已知数列{an}的前n项和sn满足sn=an^2+bn,求证{an}是等差数列 已知等差数列{an}满足a1=3.a4+a8=26,{an}的前n项和为Sn.求an及sn 已知等差数列{an}满足：a1=3,a4+a8=26,{an}的前n项和为Sn,求an及Sn,在线等啊, 已知等差数列{an}满足:a3=7,a1＋a11=26,{an}的前n项和为Sn,求an及Sn 等差数列an的前n项和为Sn,已知Sm=a,Sn-Sn-m=b,m、n属于自然数且n>m,求Sn? 已知等差数列an的前n项和为Sn,且满足a2+a4=14,S7=70 已知等差数列an的前n项和sn,满足sn=n²+2n+a 则实数a=