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Homework Help: Roots of a polynomial (simple!)

  1. Jul 16, 2008 #1
    [tex]x^3-7x^2-10x-8 = 0[/tex]

    what are the roots?? Sorry, Im horrible at doing these kinds of things, this is for another problem in my differential equations thread.

    Its been so long since I did simple roots of a polynomial, I forgot how to do it LOL! and please, this homework is due tomorrow morning, so if you can help please spare the lesson until tomorrow afternoon. I need this done by tonight, preferably right now. Thanks!
  2. jcsd
  3. Jul 16, 2008 #2
    Use p/q method to factor.
  4. Jul 16, 2008 #3
    elaborate please! I havent done simple algebra like this in like 2-3 years!

    I was thinking synthetic division. Would that work?
  5. Jul 16, 2008 #4
    Jesus Christ!!! I had the wrong polynomial!!

    this is the right one.

    [tex]x^3-7x^2+6x-8 = 0[/tex]
  6. Jul 16, 2008 #5


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    You'd probably need to look for that formula to find the roots of a cubic polynomial since I believe that doesn't have rational roots.
  7. Jul 16, 2008 #6
    yeah, 2 roots are imaginary, and 1 root is real.

    The three roots are according to my calculator, 6.244297529863042, 0.37785123506847906 + i* 1.06695706407035, and 0.37785123506847906 - i* 1.06695706407035.

    But theres gotta be a nicer way of writing that...
  8. Jul 16, 2008 #7


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    Check here and see if you can write it in a better way.
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