I have a bijection problem that I cannot get my head around. It goes like this:
let f: A -> B and g: B -> C be functions such that g o f is a bijection. Prove that f must be one-to-one and that g must be onto. And also an example showing that it is possible for neither f nor g to be a bijection.
This is the problem. I do not even know where to begin. Any help is appreciated.