设数列{an}前n项和为Sn,若s1=1,s2=2,且Sn+1-3Sn+2Sn-1=0(n>=2,且n∈N^*)判断数列
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s(n+1)-2sn=sn-2s(n-1)
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s(n+1)-2sn=s2-2s1=0
s(n+1)=2sn
sn为首项为1公比为2的等比数列.
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