数列{an}的前n项和为Sn,Sn=1-2/3an,则an=_.
数列{an}的前n项和为Sn,Sn=1-
an,则an=______.
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数学人气:437 ℃时间:2020-05-19 08:15:53
优质解答
∵数列{an}的前n项和为Sn,Sn=1-23an,∴a1=s1=1-23a1,解得 a1=35.且n≥2时,an=Sn-Sn-1=(1-23an)-(1-23an-1)=23an-1-23an,化简可得 anan−1=25.故数列{an}是首项为35,公比为25的等比数列,故 an=35×...
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