Comse 072 Extra Credit Problem (due November 13.)
(3 pts) It is well known that 3, 4, and 5 form a so-called Pythagorean triple in the
sense that $3^2 + 4^2 = 5^2$. Prove that if a, b, and c are any three integers with
$a^2 + b^2 = c^2$ then at least one of the integers a, b, and c is divisible by 3, one of
them (could be the same one), is divisible by 4, and one of them (again could be
the same one) is divisible by 5.
Hint: look at cases for a, b, and c modular 3, 4, and 5, respectively.