Help needed, much appreciated

What is the frequency of the sinusoidal graph?

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.

Pl approximate the value of 13−−√ to the nearest tenths place. plot the approximation on the number line.