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Homework Help: Find when 2x^3+x-5 is equal to zero

  1. Sep 14, 2004 #1
    I need to find when 2x^3+x-5 is equal to zero and I'm stuck

    2x^3+x-5=0
    5=2x^3+x....then what?
     
  2. jcsd
  3. Sep 15, 2004 #2

    Hurkyl

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    You sure you have the right problem?


    There is a really nice theorem for finding all of the rational zeroes of a polynomial that involves the first and last terms of the polynomial, have you seen it yet?
     
  4. Sep 15, 2004 #3

    HallsofIvy

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    Hurkyls method show that there are no rational solutions. That means that this cannot be factored with integer coefficients. There is a "cubic formula" but it is very messy. It is probably best solved numerically.

    (The method I used was to graph it on my calculator, then "zoom" in on the x-intercept!)
     
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