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Homework Help: Help with a Proof

  1. Sep 12, 2013 #1
    1. The problem statement, all variables and given/known data

    Prove for all xεR [(-x)3 = -(x3)]
    (Hint you may use the fact that -x = (-1)*x, but other wise stick to axioms)
    I wrote something along the lines of .
    (-x)3 can be written as (-1)(x)(x)(x) and -(x)3 can be written as (-1)((x)(x)(x))
    and these are both equivalent
    But it doesn't feel like I'm proving anything.
    Not sure how to really write this out so there is enough "proof"
  2. jcsd
  3. Sep 12, 2013 #2


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    Science Advisor

    I think the point you are missing is that (-x)3 "can be written as" (-x)(-x)(-x) and then you can show that is equal to -(x)(x)(x).
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