已知等比数列的Sm=30,前2m项和为S2m=90,求S3m的值
在等差数列{an}中,公差为d,顺次m项和Sm,S2m-Sm,S3m-S2m,.组成公差为______的等差数列
已知{an}是等差数列,前n项和记为Sn,已知数列Sm,求证:Sm,S2m-Sm,S3m-S2m也成等差数列
已知等比数列an中,Sm=10 S2m=30
(2014•安徽模拟)已知等比数列{an}的前n项和为Sn,若Sm+3-Sm+2=8(Sm-Sm-1)(m>1,m∈N)
等差数列{an}的前n项和为Sn,已知am-1 +am+1 -(am)^2=0,S2m-1=38,求m
等差数列(an),前n项和为Sn.(1)Sm=n,Sn=m.求Sm+n的值(2)Sm=Sn(m不等于n)求Sm+n的值
已知等比数列{an}的前n项和为Sn,若am,am+2,am+1(m∈R)成等差数列,试判断Sm,Sm+2,S
等差数列an前n项和为Sn=m,Sm=n,求Sm+n的值
已知等比数列an的前n项和为sn,若Sm,Sm+2,Sm+1成等差数列,证明amam+2,am+1成
等差数列{an}的前n项和为Sn,已知am-1+am+1-am2=0,S2m-1=38,则m等于
已知等比数列{an}的前n项和为Sn,若am,am+2,am+1(m∈R)成等差数列,试判断Sm,Sm+2,Sm+1 是
Sn为等差数列的前n项和,Sn=m,Sm=n,求:Sm+n