高一简单数列

a（n+1）=3an+4
两边加2得
a（n+1）+2=3an+6
a（n+1）+2=3(an+2)
所以an+2是以首项为a1+2=3公比q=3的等比数列

所以an+2=3*3^（n-1）=3^n
所以an=3^n-2

A(n+1)=3An+4

[A(n+1)+2]=3[An+2]

令An+2=Bn，

Bn=3^(n-1)*B1

An+2=3^(n-1)*(A1+2)

An=3^n-2
纯手工做答

A(n+1) = 3An+4
A(n+1)+2 = 3(An+2)
{An+2}是等比数列, 公比为3
An+2 = 3^(n-1) (A1+2) = 3^n

An = 3^n-2
(3的n次方-2)