1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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

    HallsofIvy

    User Avatar
    Staff Emeritus
    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).
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Help with a Proof
  1. Help with proofs (Replies: 6)

  2. Help with a proof. (Replies: 10)

  3. Proofs help (Replies: 7)

  4. Help with a proof! (Replies: 8)

  5. Proof help! (Replies: 3)

Loading...