Proofs - Discrete Mathematics
discrete.openmathbooks.org › dmoi2 › sec_logic-proofsProofs Discrete MathematicsAn Open Introduction 3.2Proofs ¶ Investigate! Decide which of the following are valid proofs of the following statement: If ab is an even number, then a or b is even. Suppose a and b are odd. That is, a = 2k + 1 and b = 2m + 1 for some integers k and m. Then ab = (2k + 1)(2m + 1) = 4km + 2k + 2m + 1 = 2(2km + k + m) + 1.