设等差数列an公差为d,等比数列bn公比为qa1=b1a3=b3 => a1+2d=b3=a1*q^2a7=b5 => a1+6d=b5=a1*q^4b3²=b1*b5 => (a1+2d)²=a1*(a1+6d) =>a1=2d所以b3=a3=4d,b5=a7=8d因为bn是各项为正的等比数列,所以q=√(b5/...