1. Here is the problem I'm stuck on: Let q be a positive integer, q is greater than or equal to 2, let a and b be integers such that if q divides ab, then q divides a or q divides b. Show that q is a prime number. 2. I know that q is prime if and only if 1 divides q and q divides q. 3. I don't really know where to begin. Where might I go from here?