Which of the following best describes set of numbers? 6, 9, 12, 15, infinite alternating sequence finite geometric sequence infinite arithmetic series infinite arithmetic sequence?

Let x have probability generating function gx (s) and let un generating function u(s) of the sequence uo, u1, satisfies p(x > n). show that the (1- s)u(s) = 1 - gx(s), whenever the series defining these generating functions converge.