题目内容
设等比数列{an}的前n项和为Sn,若
=4,则
=__________( )
s6 |
s3 |
s9 |
s6 |
A.2 | B.
| C.
| D.3 |
由等比数列的性质可得S3,S6-S3,S9-S6仍成等比数列,
∵
=4,∴S6=4S3,∴S3,3S3,S9-4S3成等比数列,
∴S9-4S3=9S3,解得S9=13S3,
∴
=
=
故选:C
∵
S6 |
S3 |
∴S9-4S3=9S3,解得S9=13S3,
∴
S9 |
S6 |
13S3 |
4S3 |
13 |
4 |
故选:C
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