S3=a1+a2+a3=14/3S6-S3=a4+a5+a6=112/3a4/a1=a5/a2=a6/a3=q³所以(a4+a5+a6)/(a1+a2+a3)=q³=8q=2所以a1+a2+a3=a1+a1q+a1q²=a1(1+q+q²)=7a1=14/3a1=2/3所以an=(2/3)*2^(n-1)=(2^n)/3