Contrapositive Approach to Domain/Range Proof
Let \(f: A \rightarrow B\) be a function such that if \(x \in A\) then \(f(x) \in B\). Prove that if \(f(x) \notin B\), then \(x \notin A\) using a contrapositive argument.
Contrapositive Proof of an Integer Property
Prove the following statement using the contrapositive approach: “If an integer squared is even, then the integer is even.”