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Thread: PROOF by counterexample

  1. October 4th 2010, 04:08 PM #1
    mremwo
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    PROOF by counterexample

    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; October 4th 2010 at 04:12 PM. Reason: actually i want to know how to EITHER give a counterexample OR proveone/ both directions
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