Contrapositive - if p is prime, then if p|ab then p|a or p|b (Euclid's lemma)
a = p1, b = p/p1
The contrapositive states that p is prime, and p1 is a prime divisor of p. That means that p1 must equal 1 or p.
Case 1: p1 = 1, a = 1, b = p
p|ab = p|p
p|a = p|1
p|p is true
So that means the...