Irrational and rational proofs

Hey, I was wondering about proving that square roots of numbers are rational or irrational.
I know about proving this for the numbers 1(duh), 2 and all multiples of 2 and 4, but what about 3?
How do i prove that 3(or any other number) is irrational or rational?

>>26
lol idiot.  For someone obsessed with proof, you sure do make unfounded claims.