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各项均为正数的等比数列{an}的前n项和为Sn,若Sn=2,S3n=14,则S4...
各项均为正数的等比数列{an}的前n项和为Sn,若Sn=2,S3n=14,则S4n等于( )
A.80
B.30
C.26
D.16
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