a(n+1)+x=3/2an+1+x=3/2(an+2/3+2/3*x]
则令x=2/3+2/3*x
x=2
所以
a(n+1)+2=3/2(an+2)
所以an+2是等比数列
令bn=an+2
q=3/2
b1=a1+2=3
bn=3*(3/2)^(n-1)
则an=-2+3*(3/2)^(n-1)