Verified answer

b1 = 1/9

b5 = b1*q^4 = 9

b5/b1 = 9 : 1/9 = 81

q^4 = 81

q = +- 3

1. q = 3

b2 = b1*q = 1/9*3 = 1/3

b3 = b2*q = 1/3*3 = 1

b4 = b3*q = 1*3 = 3

2. q = -3

b2 = b1*q = 1/9*(-3) = -1/3

b3 = b2*q = (-1/3)*(-3) = 1

b4 = b3*q = 1*(-3) = -3