等差数列中,已知前n项和Sn=5n^2+3n,则通项an?

已知等差数列前n项和 sn=2n^2+3n求an 等差数列{an}中,已知前n项和sn=5,前2n项和s2n=20,则求前3n项和s3n 已知等差数列{an}前n项和Sn=-2n^2-n 等差数列{an}前n项和为Sn=3n-2n^2,求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}的前n项和Sn=3n²-2n,证明数列{An}为等差数列 已知等差数列an中,a1=1,前n项和Sn,若S(n+1)/Sn=(4n+2)/(n+1),求an 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 已知等差数列{an}的前n项和为Sn,且(2n-1)Sn+1 -(2n+1)Sn=4n²-1(n∈N*) 已知数列{an}前n项和为sn=3n^2-n,求证其为等差数列 已知等差数列an中,a1=1 前n项和SN满足条件S（2n-1)/Sn=4n-2/n+1 已知an=5n(n+1)(n+2)(n+3),求数列{an}的前n项和Sn