记等差数列{an}前n项和为Sn,求证{Sn/n}为等差数列?若a1=1且对任意正整数n,k n>k 都有根号下[S（n+k)]+根号下[S(n-k)]=2根号下（Sn)成立,求{an}通项公式记bn=a^(an) 就是a的an次方,a>0求证( b1+……bn)/n≤（b1

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}前n项和为sn,求证S2n-1=(2n-1)an 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 等差数列前n项和为Sn,求证:S2n-1=(2n-1)an 等差数列{an}前n项和为Sn,求证S 2n-1项=（2n-1）an 已知数列{an}的前n项和为Sn=n^2-3n,求证：数列{an}是等差数列 已知数列an前n项的和sn＝n²－9n求证an为等差数列 等差数列an前n项和为Sn,求证S（2n-1）=（2n-1）an 已知数列{an}的前n项和Sn=-n^2+18n,求证:{an}为等差数列 已知数列an的前n项和为sn,且sn=n^2-16n n∈ N*1.求证an是等差数列2.记bn=绝对值an,求数列bn的前n项和Tn 等差数列{an}的前n项和为sn,a10 设Sn为等差数列前n项和,求证:{Sn/n}是等差数列 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 已知数列｛an｝前n项和为Sn,对于n属于自然数,总有Sn=(a1+an)n/2,求证｛an｝为等差数列. 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 已知数列{an}前n项和为sn=3n^2-n,求证其为等差数列