设数列{An}的前n项和为Sn,且满足Sn=2An-3n,n=1,2,3……(1)设Bn=An+3,求证:数列{Bn}是
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设数列{An}的前n项和为Sn,且满足Sn=2An-3n,n=1,2,3……(1)设Bn=An+3,求证:数列{Bn}是等比数列;...
设数列{An}的前n项和为Sn,且满足Sn=2An-3n,n=1,2,3……(1)设Bn=An+3,求证:数列{Bn}是等比数列;(2)求数列{An}的通项式;(3)求数列{nFn}的前n项和Tn
设数列{An}的前n项和为Sn,且满足Sn=2An-3n,n=1,2,3……(1)设Bn=An+3,求证:数列{Bn}是等比数列;(2)求数列{An}的通项式;(3)求数列{nFn}的前n项和Tn
Sn=2An-3n,Sn-Sn-1=An=2An-3n-2An-1+3(n-1),An=2An-1+3.
令n=1,有A1-3=0,A1=3;B1=6
(1)An=2An-1+3所以(An+3)=2(An-1+3),Bn=2Bn-1所以是等比数列
(2)由(1),Bn通项为Bn=6*2^(n-1),所以An=6*2^(n-1)-3
令n=1,有A1-3=0,A1=3;B1=6
(1)An=2An-1+3所以(An+3)=2(An-1+3),Bn=2Bn-1所以是等比数列
(2)由(1),Bn通项为Bn=6*2^(n-1),所以An=6*2^(n-1)-3
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