问题标题:
等比数列{an}的前n项和为Sn,已知S1,S3,S2成等差数列(Ⅰ)求{an}的公比q;(Ⅱ)a1-a3=3,求Sn.
问题描述:
等比数列{an}的前n项和为Sn,已知S1,S3,S2成等差数列
(Ⅰ)求{an}的公比q;
(Ⅱ)a1-a3=3,求Sn.
耿平回答:
(Ⅰ)∵等比数列{an}的前n项和为Sn,
S1,S3,S2成等差数列,
∴2(a1+a1q+a
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