First to type your question in LaTeX:
Show that if , and is an odd prime, then or .
I think that one route to try comes from the observation that the GCD of and divides any "linear combination" of them; that is, it will divide any number of the form for any integers . So, in particular, must divide
The nice part is that this shaves off and from the numerator and leaves you with terms that look like where ranges between and . And in particular, you may know that this kind of term is divisible by , which seems helpful for your statement.
Maybe you can play around with this for a while and see where it goes.