已知各项为正,公比为√3的等比数列{an}的前n项和为Sn,记bn=(S3n+26S2n)/an+1Sn,求bn的最小项

a1,...,an=a1(√3)^(n-1)Sn=a1(1-√3^n)/(1-√3)bn={a1[1-√3^(3n)]/(1-√3)+26a1[1-√3^(2n)]/(1-√3)}/[(a1√3^n)a1(1-√3^n)/(1-√3)]={[1-√3^(3n)]+26[1-√3^(2n)]}/[a1(√3^n)(1-√3^n)]={[1+√3^n+√3^(2n)]+...