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Direct proofs help

  1. Jun 12, 2012 #1
    Let nεZ,Prove that 1-n^2>0, then 3n-2 is an even integer.

    I proved it like this. I think its right but im not able to word it correctly.

    Since 1-n^2>0 therefore n=0. Then 3n-6=3(0)-2=-2. Since 0 is an integer, 3n-6 is even.

    How can I learn to word this correctly because im having some trouble with it?
    Last edited: Jun 12, 2012
  2. jcsd
  3. Jun 12, 2012 #2


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    Are you sure you have the statement of the problem correct? It looks crazy. As you say 1 - n2 > 0 would imply n = 0, which makes the rest of it much too easy. Also, why would anyone ask you to prove 3n-2 is an even integer when n is already known to be an integer? Why not just ask you to show n is even?
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