Find g(x)) when f(x) = 3x2 + x - 8, and g(x) = 4x + 5 I have no idea what she’s talking about please help me out

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.