已知等比数列的n项和为Sn,若S6/S3=3.求s9/S6=?,
来源:学生作业帮 编辑:搜搜做题作业网作业帮 分类:数学作业 时间:2024/05/17 00:52:03
已知等比数列的n项和为Sn,若S6/S3=3.求s9/S6=?,
S6=a1(q^6-1)/(q-1)
S3=a1(q^3-1)/(q-1)
S6/S3=(q^6-1)/(q^3-1)=3
(q^3+1)(q^3-1)/(q^3-1)=3
q^3+1=3
q^3=2
S9=a1(q^9-1)/(q-1)
所以S9/S6=(q^9-1)/(q^6-1)
=(q^3-1)(q^6+q^3+1)/(q^3+1)(q^3-1)
=(q^6+q^3+1)/(q^3+1)
=(4+2+1)/(2+1)
=7/3
S3=a1(q^3-1)/(q-1)
S6/S3=(q^6-1)/(q^3-1)=3
(q^3+1)(q^3-1)/(q^3-1)=3
q^3+1=3
q^3=2
S9=a1(q^9-1)/(q-1)
所以S9/S6=(q^9-1)/(q^6-1)
=(q^3-1)(q^6+q^3+1)/(q^3+1)(q^3-1)
=(q^6+q^3+1)/(q^3+1)
=(4+2+1)/(2+1)
=7/3
设等比数列an的前n项的和为Sn,若S6/S3=3,则S9/S6=
1.设等比数列{an}的前n项和为Sn,若S6/S3=3,则S9/S6=?
已知正项等比数列{an}的前n项和为Sn,若S3=3,S9-S6=12,则S6=______.
设等比数列{an}的前n项和为Sn,若S6:S3=1:2,则S9:S3=?
等比数列前n项和Sn,S6/S3=3,S9/S6=?
等比数列{an}的前n项和为sn,若S3,S9,S6成等差数列,求此数列的公差,
设等比数列{an}的前n项和为sn,若S6,S9,S3成等差数列,问2S3,S6,S12-S6S能否成等比数列?请说明理
设等比数列an的前n项的和为Sn,若S6/S3=1/2,则S9/S3=
已知Sn是等比数列{An}的前N项和,S3,S9,S6成等差数列,则
已知等比数列{An}的公比为q,前n项的和为Sn,且S3,S9,S6成等差数列.
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=( )
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