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.