In: Advanced Math
Prove the following theorem:
Theorem
∀n ∈ Z, n is either even or odd (but not both).
Your proof must address the following points:
1. n is even or odd (and nothing else).
2. n is odd =⇒ n is not even (hint: contradiction).
3. n is even=⇒ n is not odd (hint: contrapositive).
The first point is a bit more difficult. Start by making a statement about 0. Then assuming that n is even, what can you say about n−1 and n+ 1? Likewise, assuming that n is odd, what can you say about n−1 and n+ 1. Can you organize these facts into an argument that shows that you have accounted for all possible n ∈ Z?