Prove Theorem 1a (below) with an indirect proof (using cases). For each variable that appears in your proof, you must state what that variable...

 Prove Theorem 1a (below) with an indirect proof (using cases).

For each variable that appears in your proof, you must state what that variable represents. For each step in your proof, it must be made clear to the reader whether it is an assumption, something you are about to prove, or something that follows from a previous step or a denition.

Theorem 1a. Let n be an integer. If 7 divides n2, then 7 divides n.