摘要:解:当n=1时.S1=2a1-1=a1 ∴a1=1 -------------------------------------------------------------------------------2分当n≥2时an=Sn-Sn-1=2an-1-2an-1 +1-----------------------------6分∴an=2an-1--------------------------------------------------------8分∴{an}是以1为首项.以2为公比的等比数列 ----------------------9分∴an=1×2n-1=2n-1 ---------------------------------------------10分
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