设sn为等比数列an的前n项和,2a3-a4=0,S5/a1=
设sn为等比数列an的前n项和,2a3-a4=0,S5/a1=
设{an}是等差数列,{bn}是等比数列,记{an}{bn}的前n项和分别为Sn,Tn若a3=b3,a4=b4,且(S5
已知等差数列{an}前n项和为Sn,公差d≠0,且S3+S5=50,a1,a4,a13,成等比数列 设{bn/an}是首
已知等差数列{an}的前n项和为Sn,公差d≠0,S5=4a3+6,且a1,a3,a9成等比数列.
设等比数列的前n项和为sn,a4=a1-9,a5,a3,a4成等差数列
1.已知等比数列{an}中,设Sn为其前n项和,a1+a3=10,a4+a6=5/4,求其第4项及第5项和S5.2.设{
已知数列{an}为等比数列,Sn是它的前n项和,若a2×a3=2a1,且a4与2a7的等差中项为4\5,则S5=?...
已知数列{an}为等比数列,Sn是它的前n项和,若a2•a3=2a1,且a4与2a7的等差中项为54,则S5=( )
已知数列{an}为等比数列,Sn是其前n项和.若a2*a3=2a1且a4与2a7的等差中项为5/4,则S5=?
设等比数列{an}的前n项和为Sn,若S10:S5=1:2,求S15:S5
已知等差数列{an}的前n项和为Sn,公差d≠0,且S3+S5=50,a1,a4,a13成等比数列.
已知等差数列{an}前n项和为Sn,公差d≠0,且S3+S5=50,a1,a4,a13,成等比数列 (2)若从数列