give a counterexample for each of the two directions of: The product xy of a rational number x and a real number y is irrational if and only if y is irrational. cant figure out the first direction
Last edited by mremwo; Oct 4th 2010 at 05:12 PM. Reason: actually i want to know how to EITHER give a counterexample OR proveone/ both directions
Follow Math Help Forum on Facebook and Google+