(2014•南宁二模)设等比数列{an}的前n项和为Sn,若a1=1,S6=4S3,则a10=______.
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(2014•南宁二模)设等比数列{an}的前n项和为Sn,若a1=1,S6=4S3,则a10=______.
![(2014•南宁二模)设等比数列{an}的前n项和为Sn,若a1=1,S6=4S3,则a10=______.](/uploads/image/z/8235258-42-8.jpg?t=%EF%BC%882014%E2%80%A2%E5%8D%97%E5%AE%81%E4%BA%8C%E6%A8%A1%EF%BC%89%E8%AE%BE%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97%7Ban%7D%E7%9A%84%E5%89%8Dn%E9%A1%B9%E5%92%8C%E4%B8%BASn%EF%BC%8C%E8%8B%A5a1%3D1%EF%BC%8CS6%3D4S3%EF%BC%8C%E5%88%99a10%3D______%EF%BC%8E)
设等比数列{an}的公比为q,
显然q=1,不满足S6=4S3,
故可得
1-q6
1-q=4×
1-q3
1-q,
解之可得q3=-4,
∴a10=1×(-4)3=-64.
故答案为:-64.
显然q=1,不满足S6=4S3,
故可得
1-q6
1-q=4×
1-q3
1-q,
解之可得q3=-4,
∴a10=1×(-4)3=-64.
故答案为:-64.
(2014•南宁二模)设等比数列{an}的前n项和为Sn,若a1=1,S6=4S3,则a10=______.
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