Exercise 2.5.1: Proofs by cases Prove each statement If x is an integer, then x2+5x-1 is odd. If x and y are real numbers, then max(x, y) + min(x, y)xy c) If integers x and y have the same parity, then x + y is even. The parity of a number tells whether the number is odd or even. If x and y have the same parity, they are either both even or both odd For any real number x, Ix) 20