数列{an}中,Sn-2an=2n, 求证{an-2}是等比数列
数列{an}中,前n项和Sn=2n-1,求证:{an}是等比数列.
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
数列an的前n项为sn,已知2an-2^n=sn.求证an-n·2^(n-1)是等比数列
已知在数列an中,Sn=2n^2+3n,求证an是等差数列
已知数列an的前n项和Sn=4-4*2的-n次方,求证an是等比数列
数列{an}中,a1=1,Sn+1=4an+2设bn=an+1-2an,求证{bn}是等比数列,并求{an}通项.
数列{an}前n项和为Sn,且an+Sn=-2n-1 证明{an+2}是等比数列
已知数列{an}的前n项和Sn满足条件Sn=3an+2,①求证数列{an}成等比数列②求通项公式an
设数列{an}的前n项和为Sn=2an-4,bn=log2an,cn=1/bn^2,求证:数列{an}是等比数列?
数列{an}中,a1=1,Sn+1=4an+2设bn=an+1-2an,求证{bn}是等比数列,设cn=an/3n-1,
数列{an}中,a1=1,Sn+1=4an+2设bn=an+1-2an,求证{bn}是等比数列,并求其通项.
已知数列{an}满足Sn=2n-an(n属于N*),证明{an-2}是等比数列