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},Sn是其前n项和,且满足3An=2Sn+n,n为正整数,求证数列{An+1/2}为等比数列 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项和为sn=3n^2-n,求证其为等差数列 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}的前n项和为Sn,且满足Sn=Sn-1/2Sn-1 +1,a1=2,求证{1/Sn}是等差数列 已知数列an的前n项和为sn,且sn+an=n^2+3n+5/2,证明数列{an-n}是等比数列 已知数列｛an｝的前n项和sn=n方+3n,求证数列{an}是等差数列 已知数列{an}中,a2=2,前n项和为Sn,且Sn=n(an+1)/2证明数列{an+1-an}是等差数列 已知数列｛An｝的各项均为正数,前n项和为Sn,且满足2Sn=An²+n-4 1.求证｛An｝为等差数列 高一数学问题：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}得前n项和为sn=an^2+bn(a,b为常数且a不等于0)求证数列{an}是等差数列