I am trying to learn how to write proofs and this proof seems weird...
Suppose f o g = I. Prove that every number b can be written b = f(a) for some number a.
The Attempt at a Solution
Here's my stab at it.
This really doesn't seem sufficient to me however. What I'm trying to say is that I can choose x to equal any number b. With the application of g upon x=b I get some number a. Then with the application of f upon a i get back the number I wanted, namely b.