设sn是等差数列｛an｝的前n项和,1/3S3与1/4S4的等比中项为1/5S5,1/3S3与1/4S4的等差中项为1,求通项an

设Sn为等差数列{An}的前n项和,求证：{Sn/n}是等差数列 设Sn为等差数列an的前n项和.求证Sn/n为等差数列 设Sn是等差数列{an}的前n项和,且S5S8,则a1 设Sn是等差数列｛an｝的前n项和,求证：若正整数m,n,p成等差数列,则Sm/m,Sn/n,Sp/p也成等差数列. 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 设Sn是等差数列an的前n项和,若S3/S7=1/3,则S6/S7= 设Sn是等差数列An的前n项和,若S3/S6=1/3,则S6/S12等于 设Sn是等差数列an的前n项和,若S3/S6=1/3,则S6/S7=? 设Sn是等差数列{an}的前n项和,若S3/S6=1/3,求S6/S12 设Sn是等差数列(An)的前n项和,若S3/S6=1/3,求S6/S12=? 设Sn是等差数列{An}的前n项和,若S3/S6=1/3,则S6/S12=? 1.设Sn是等差数列【An]的前n项和,若S3/S6=1/3,求S6/S12 设Sn是等差数列an的前n项和,s4/s12=1/6 则s8/s16=? 设Sn是等差数列{an}的前n项和,若S3/S6=1/4,则S6/S12等于? 设Sn是等差数列{an}的前n项和,若S3/S6=1/3,则S6/S12=? 设Sn为等差数列{an}的前n项和,已知a6+a70,那么Sn中最小的是 设Sn为等差数列{an}的前N项和,已知 a6 +a70,那么Sn 中最小的是 设等差数列{an}的前n项和为Sn 若a1=Sn>