Prove by cases:
1) Statement: If ? ∈ ℤ, then ?
? + ?? + ? is an odd integer.
Proof:
2) Statement: If ? ∈ ℤ, then ?
? − ? is even.
Prove:
3) Prove the following statement by Proof by Contrapositive, and Proof by Contradiction:
Statement: If ?? − ? is odd, then ?? + ? is even