Hi Tony,
I think your claim should be considered as a corallary. That is an obvious result after a proof or lemma has been proven.
It is clear that if a, b, and c are real numbers, then there will a solution. Thus no proof is required. Irrational number is a subset of real number.
It's the integer part that made FLT difficult to prove. Many amateur and seasoned mathematicians approached FLT as a^n+b^n-c^n=0. That leads to solve equation of 3 unknowns. Direct approch proof would be impossible. Thus the indirect proofs have been devised. For example, elliptic curve (I called it fancy geometry). I know very little about it. But it is a big thing for math gurus.
Cheers,
flt4fun