已知数列an,an>0,Sn=a1+a2+a3.+an,且an=6Sn/an + 3,求Sn!
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已知数列an,an>0,Sn=a1+a2+a3.+an,且an=6Sn/an + 3,求Sn!
已知数列an,an>0,Sn=a1+a2+a3.+an,且an=6Sn/an + 3〔不是a(n+3),是an + 3,〕求Sn!
已知数列an,an>0,Sn=a1+a2+a3.+an,且an=6Sn/an + 3〔不是a(n+3),是an + 3,〕求Sn!
An=6Sn/(An+3)
6Sn=(An)^2+3An
n>=2
6S(n-1)=(A(n-1))^2+3A(n-1)
6An=(An)^2+3An-(A(n-1))^2-3A(n-1)
(An)^2-(A(n-1))^2=3An+3A(n-1)
(An+A(n-1))(An-A(n-1))=3(An+A(n-1))
An>0
An+A(n-1)≠0
An-A(n-1)=3
6A1=6S1=(A1)^2+3A1
A1=3
{An}是3为首项,3为公差的等差数列
An=3n
6Sn=(An)^2+3An
n>=2
6S(n-1)=(A(n-1))^2+3A(n-1)
6An=(An)^2+3An-(A(n-1))^2-3A(n-1)
(An)^2-(A(n-1))^2=3An+3A(n-1)
(An+A(n-1))(An-A(n-1))=3(An+A(n-1))
An>0
An+A(n-1)≠0
An-A(n-1)=3
6A1=6S1=(A1)^2+3A1
A1=3
{An}是3为首项,3为公差的等差数列
An=3n
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