an为等差数列,sn为等差数列前n项和,s7=7,s15=75,设Tn为数列sn/n的前n项和,求Tn

设Sn为等差数列an的前n项和.求证Sn/n为等差数列 设Sn为等差数列{An}的前n项和,求证：{Sn/n}是等差数列 等差数列{an}的前n项和为sn,a10 等差数列{an}前n项和为Sn=3n-2n^2,求an (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 等差数列前n项和为Sn=1/2(An+1/An),求通项An 等差数列{an}前n项和为sn,求证S2n-1=(2n-1)an 设等差数列{an}的前n项和为Sn 若a1=Sn> 已知an是等差数列,前n项和为Sn,求证:S3n=3(S2n-Sn) 一道关于等差数列的题设Sn为等差数列｛An｝的前n项和 求证：数列｛n分之Sn}是等差数列 等差数列前n项和为Sn,求证:S2n-1=(2n-1)an 记数列{an}的前n项和为Sn,若{Sn/an}是公差为d的等差数列,则{an}为等差数列的充要条件是d=? 等差数列An中Sn为前n项和,a4+a7=10,则S10为 an为等差数列,Sn为前n项和,S8-S3=10,问S11=? 设Sn为等差数列前n项和,求证:{Sn/n}是等差数列 已知等差数列an中,前n项和sn=n^2-15n,则使sn为最小值的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