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已知数列{an}是等差数列,a2=6,a5=18;数列{bn}的前n项和是Tn,且Tn+b...
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已知数列{a
n}是等差数列,a
2=6,a
5=18;数列{b
n}的前n项和是T
n,且T
n+
b
n=1.
(1)求数列{a
n}的通项公式;
(2)求证:数列{b
n}是等比数列;
(3)记c
n=a
n•b
n,求{c
n}的前n项和S
n.
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已知数列{an}是等差数列,a2=6,a5=18;数列{bn}的前n项和是Tn,且Tn+bn=1.
(1)求数列{an}的通项公式;
(2)求证:数列{bn}是等比数列;
(3)记cn=an•bn,求{cn}的前n项和Sn.
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已知数列{an}是等差数列,a2=6,a5=18;数列{bn}的前n项和是Tn,且Tn+bn=1.
(1)求数列{an}的通项公式;
(2)求证:数列{bn}是等比数列;
(3)记cn=an•bn,求{cn}的前n项和Sn.
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(1)求数列{an}的通项公式;
(2)求证:数列{bn}是等比数列;
(3)记cn=an•bn,求{cn}的前n项和Sn.
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(2)求证:数列{bn}是等比数列;
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(2)求证:数列{bn}是等比数列;
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