n=1时,2^(1-1) ×a1=S1=9-6×1a1=3n≥2时,2^(n-1)×an=Sn-S(n-1)=9-6n-[9-6(n-1)]=-6an=-6/2^(n-1)=-3/2^(n-2)n=1时,a1=-3/2^(1-2)=-6≠3,不满足通项公式数列{an}的通项公式为an=3 n=1-3/2^(n-2) n≥2...