Prove the following statement directly from the definition of rational number. The difference of any two rational numbers is a rational number. Proof: Supposer and s are any two rational numbers. By definition of rational, r = and s= for some ---Select--- a b d Writer - s in terms of a, b, c, and d as a quotient of two integers whose numerator and denominator are simplified as much as possible. The result is the following. r-s= Both the numerator and the denominator are integers because ---Select--- In addition, bd 0 by the ---Select--- Hence r - s is a ---Select--- of two integers with a nonzero denominator, and so by definition of rational, r- s is rational. ✓a, b, c, and d with ---Select---