Math Help - functions

1. functions

A,B,C are sets and f: A-->B and g: B-->C. Prove:

1)If f and g are one-to-one, then so is g o f.
2)If g o f is one-to-one, then g need not be one-to-one.

gof(x) = gof(y) $\rightarrow$ x = y