若{an}为等差数列,Sn是其前n项和.且S
已知数列an其前n项和为Sn,且Sn=3n^2+5n,求证数列an是等差数列
已知数列{an}中,其前n项和为Sn,且n,an,Sn成等差数列(n∈N*).
两等差数列{an}和{bn},前n项和分别为Sn,Tn,且S
数列an是公差d不等于0的等差数列,其前n项和为Sn,且
{an},{bn}是两个等差数列,其前n项和分别为Sn和Tn,且Sn/Tn=(7n+2)/(n+3),则a8/b8=
设等差数列{an}的前n项和为Sn,且S
若两个等差数列{an}和{bn}的前n项和分别为Sn和Tn,且满足S
已知等差数列{an},sn为其前n项和,且s10=S20,则S30=______.
已知数列{an}的各项均为正数,其前n项和为Sn,若{log2an}是公差为-1的等差数列,且S6=38
在等差数列{an}中,Sn为其前n项和,且a1=13,S3=Sn
若两个等差数列{an},{bn}的前n项和分别为Sn,Tn,且满足S
已知数列{an}是公差不为零的等差数列,其前n项和为Sn,且S5=30,又a1,a3,a9成等比数列.