解:1)当n>1时 b3=b1q^2 (3)
sn=1/2(3n^2+5n) (1) b6=b1q^5 (4)
s(n-1)=1/2[3(n-1)^2+5(n-1) (2) b6/b3=q^3=8
an=(1)-(2)=1/2(3n^2+5n)-1/2[3(n-1)^2+5(n-1)] q=2 b1=1
=3n^2+2n-1 bn=2^(n-1)
当n=1时,a1=s1=4 符合an=3n^2=2n-1
所以 an=3n^2+2n-1
2)cn=an/bn=(3n^2+2n-1)/2^(n-1)=