记等差数列an的前n项和为Sn,若S2n-1=(2n-1)(2n+1),则Sn=?怎么解

等差数列{an}的前n项和为sn,若sn=30,s2n=100,则s3n=（ ） 等差数列An的前n项和为Sn,若Sn=30,S2n=100,则S3n=? 记等差数列an的前n项和为Sn,若S2n-1=(2n-1)(2n+1),则Sn=?怎么解 等差数列{an}前n项和为sn,求证S2n-1=(2n-1)an Sn为等差数列（An）的前n项和 若A2n /An=(4n-1)/(2n-1) 则S2n/Sn=? Sn为等差数列（An）的前n项和 若A2n /An=(4n-1)/(2n-1) 则S2n/Sn=? Sn为等差数列{An}的前N项和,若A2n/An=4n-1/2n-1,则S2n/Sn= 已知an是等差数列,前n项和为Sn,求证:S3n=3(S2n-Sn) 1.等比数列{an}中的前n项和为Sn,S4=2,S8=6,求S12的值2.若{an}为等差数列则Sn,S2n-Sn,S3n-S2n...也成等差数列猜想:若{an}为等比数列则Sn,S2n-Sn,S3n-S2n..也称等比数列吗? 等差数列an的前n项和为Sn,且Sn=30,S2n=90,则S3n=? 等差数列前n项和为Sn,求证:S2n-1=(2n-1)an 已知等差数列an的前n项的和为Sn=48,S2n=60,S3n=? 在等差数列{an}中,已知Sn,S2n,S3n分别表示数列的前n项和,前2n项和,前3n项和.求证:Sn,S2n-Sn,S3n-S2n是等差数列 等差数列{an}的前n项和为Sn,且a2n：an=(4n-1):(2n-1),则S2n:Sn=____. 请证明：若数列{n}与{bn}都是等差数列,它们的前n项和分别为Sn,Tn,则an/bn=S2n-1/T2n-1 在等差数列{an}中,已知Sn,S2n,S3n分别表示数列的前n项和,前2n项和,前3n项和.求证:Sn,S2n-Sn,S3n-S2n是等差 等比数列an的前N项和为Sn,sn=2,s2n,则s3n=? 等差数列｛an｝｛bn｝的前n项和分别为Sn、Tn,且an:bn=2n-1:3n-1,则S2n+1：T2n+1=?