记等差数列{an}的前n项和为Sn，公比是正数的等比数列{bn}的前n项和为Tn

设公差为d，公比为q 则a3+b3=a1+2d+b1*q²=1+2d+3q²=17 2d+3q²=16 (1) T3-S3=(b1+b1*q+b1*q²)-(a1+a1+d+a1+2d) =b1*(1+q+q²)-3(a1+d) =3+3q+3q²-3-3d=12 q+q²-d=4 (2) (1)+(2)*2 5q²+2q-24=0 (5q+12)(q-