摘要：7．设{an}是等比数列.Sn是{an}的前n项和.对任意正整数n.有an+2an+1+an+2＝0.又a1＝2.则S101＝ ( ) A．200 B．2 C．-2 D．0 解析:设等比数列{an}的公比为q.因为对任意正整数.有an+2an+1+an+2＝0.an+2anq+anq2＝0.因为an≠0.所以1+2q+q2＝0.q＝-1.S101＝＝2.选择B. 答案:B

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