已知等差数列{an}的前n项和为{Sn},已知a3=5.S6=361,.求通项an

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已知等差数列{an}的前n项和为{Sn},已知a3=5.S6=361,.求通项an已知等差数列{an}的前n项和为{Sn},已知a3=5.S6=361,.求通项an已知等差数列{an}的前n项和为{S

已知等差数列{an}的前n项和为{Sn},已知a3=5.S6=361,.求通项an
已知等差数列{an}的前n项和为{Sn},已知a3=5.S6=36
1,.求通项an

已知等差数列{an}的前n项和为{Sn},已知a3=5.S6=361,.求通项an
a6=3+5d
(3+3+5d)*6*1/2=36
3*(6+5d)=36
6+5d=12
5d=6
d=1.2
an=3+1.2*(n-1)=1.8+1.2n

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