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4th order polynomials

  1. Nov 28, 2010 #1
    Hey everyone

    Im doing control engineering and was wondering what methods i could use to find the roots of a 4th order polynomial?

    For example:

    (x^4) + (8x^3) + (7x^2) + 6x = 5

    Could I seperate that into two brackets of quadratics or will i need to use a really long winded method?

    Thanks in advance for any help
     
  2. jcsd
  3. Nov 28, 2010 #2
    'order'? You mean 'degree'! Well yes there is a solution for it but it is indeed long winded. You can try to find easy solutions by try. Else use Maple or Matlab.
     
  4. Nov 28, 2010 #3

    Gib Z

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    Homework Helper

    A formula exists for 4 degree polynomials analogously to the quadratic formula, but it is very long and complicated and coding it into a program would take too much time. Just numerically approximate all the roots.
     
  5. Nov 28, 2010 #4
    Sorry, i do mean degree! Slipped up cos im working with a 4th order system.
    I was worried id have to do it the long way.
    I did use Matlab but wanted to see if I could work out the answer by hand.
    Anywat, thanks for the help guys. I really appreciate it!
     
  6. Jan 30, 2012 #5
    also check this website

    http://xrjunque.nom.es/precis/rootfinder.aspx
     
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