等差数列{an}前n项和Sn 已知lim [Sn/(n²+1）]=-a1/8（a1>0) 则Sn达到最大值时的n=__

等差数列{an}前n项和Sn 已知lim [Sn/(n²+1）]=-a1/8（a1>0) 则Sn达到最大值时的n=__ 等差数列{an}前n项和Sn 已知lim [Sn/(n²+1）]=-a1/8（a1>0) 则Sn达到最大值时的n=__ 设等差数列{an}公差d是2,前n项和为Sn,则lim(an^2-n^2)/Sn 设等差数列{an}公差d是2,前n项和为Sn,则lim(an^2-n^2)/Sn 等差数列{an} 前n项和为sn,则lim（n趋向无穷）【sn/（an^2）】=? 已知数列an是等差数列,且a1≠0,Sn为这个数列的前n项和.求1、lim nan/Sn 2、lim (Sn+Sn+1)/(Sn+Sn-1) 已知数列{an}是首项为1,公差为2的等差数列,Sn(n属于N)是数列的前n项和,则lim下面为n到无穷 Sn/n^2减1...已知数列{an}是首项为1,公差为2的等差数列,Sn(n属于N)是数列的前n项和,则lim下面为n到无穷 Sn/ 已知sn=32n-n^2求等差数列|an|的前n项和sn {an}是等差数列,a1不等于0,Sn是它前n项的和.求lim (n→∞) (Sn+S(n+1))/(Sn+S(n-1)) 已知等差数列{an}前n项和Sn=-2n2-N,求通项an的表达式 已知等差数列{an}的前n项和Sn=n²求an 已知等差数列｛an｝前n项和Sn=n平方-20n,求｛|an|｝前n项和Tn.已知等差数列｛an｝前n项和Sn=n²-20n,求｛|an|｝前n项和Tn. 已知an是等差数列,前n项和为Sn,求证:S3n=3(S2n-Sn) (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 已知an为等差数列,且a1不等於0,sn为这个数列的前n项和,求对于数列{an},lim n→∞ n*an/Sn {an}是等差数列前n项和Sn已知Sm=a Sn-Sn-m=b 求Sn 等差数列an的前n项和为Sn,lim(Sn/n^2)=-a1/9＜0,求n为何值时.sn最大 已知等差数列前n项和 sn=2n^2+3n求an