OpenStudy (phoenixfire):

Need help with a proof The theory is: if 3 divides a^2 then 3 divides a. Now, they ask for the contra-positive (p->q = ~p->~q), which will be: if 3 does not divide a then 3 does not divide a^2 So now how do you prove the contra-positive: I'm not sure whether to use proof by cases, direct proof, or any of the other methods of proof.

5 years ago
OpenStudy (anonymous):

Well I don't see what's wrong with proving the original statement and by modus tollens show that the contrapositive is true...

5 years ago
OpenStudy (anonymous):

If I was to prove anything here I would use variables and show how they factor...

5 years ago