Hank used 3 1/2 bags of seeds to plant grass in the front yard he used three times as much seed to plant grass backyard how much seed did hank need for, the back yard

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.