(1)由Sn=2/3S(n-1)+1
Sn-3=2/3[S(n-1)-3]
则Sn-3为首项为-2,公比为2/3的等比数列
则Sn=(S1-3)(2/3)^(n-1)+3
=-2*(2/3)^(n-1)+3
则an=Sn- Sn-1
=-2*(2/3)^(n-1)+3+2*(2/3)^(n-2)-3
=(2/3)^(n-1)
(2)Sn
(1)由Sn=2/3S(n-1)+1
Sn-3=2/3[S(n-1)-3]
则Sn-3为首项为-2,公比为2/3的等比数列
则Sn=(S1-3)(2/3)^(n-1)+3
=-2*(2/3)^(n-1)+3
则an=Sn- Sn-1
=-2*(2/3)^(n-1)+3+2*(2/3)^(n-2)-3
=(2/3)^(n-1)
(2)Sn