等差数列{an}中,Sn是{an}前n项的和,S6=9,S9=6,则S15=?
已知Sn是等比数列{An}的前N项和,S3,S9,S6成等差数列,则
设Sn是等比数列{an}的前n项和,S3,S9,S6成等差数列,则公比q=______.
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.
设等比数列an的前n项的和为Sn,若S6/S3=3,则S9/S6=
填空题等差数列{an}的前n项和为Sn,若S3=3,S6=9,则S9=( ).
1.设等比数列{an}的前n项和为Sn,若S6/S3=3,则S9/S6=?
已知等比数列{an}的公比为q,前n项和为Sn,且 S3,S9,S6 成等差数列,则q^3=( )
设Sn是等差数列An的前n项和,若S3/S6=1/3,则S6/S12等于
Sn是等差数列An的前N项和.A12=-8,S9=-9,则S16=多少
设Sn是等差数列{an}的前n项和,若a5/a3=5/9,则S9/S5=:
设等比数列{an}的前n项和为Sn,若S6:S3=1:2,则S9:S3=?