设sn是等差数列{an}的前n项和, 若a5:a7=2:3,求s9:(s13-s9)
设等差数列{an}的前n项和为Sn,且a5=3a7,则S9/S13=?
Sn为等差数列{an}的前n项和,S9=-36,S13=-104,等比数列{bn}中,b5=a5,b7=a7,则b6等于
3道数列题1.等差数列an的前n项 和为sn,s9=-18,s13=-52,等比数列bn中,b5=a5,b7=a7,求b
设Sn是等差数列{an}的前n项和,若a5/a3=5/9,则S9/S5=:
设等差数列[an]的前n项和为Sn,若a5=5a3,则S9/S5等于多少?
(2010•宿松县三模)等差数列{an}的前n项和为Sn,S9=-18,S13=-52,等比数列{bn}中,b5=a5,
设Sn是等差数列{an}的前n项和,若a5/a3=5/9,则S9/S5值为?
设Sn是等比数列{an}的前n项和,S3,S9,S6成等差数列,且a2+a5=2am,则m等于( )
设Sn是等比数列{an}的前n项和,S3,S9,S6成等差数列.
设等差数列 {an}的前n 项和为Sn,若S9>0 ,S10
设Sn是等比数列的前n项和,S3,S9,S6成等差数列 求证a2,a8,a5成等差数列
设Sn是等比数列{an}的前n项和,s3,S9,S6,成等差数列求证:a2,a8,a5 成等差数列