Question

a,a+b,a+b+c,a+b+c+d.成公比为q的等比数列,求q+q的平方+q的三次方

Answer 1

q=(a+b)/a,q^2=(a+b+c)/a,q^3=(a+b+c+d)/a

q+q^2+q^3=(3a+3b+2c+d)/a