Help with exact solutions of cubic root

Discussion in 'Community Discussion' started by Wes, Nov 13, 2005.

  1. Wes macrumors 68020

    Wes

    Joined:
    Jun 22, 2001
    Location:
    London
    #1
    Hello,

    I've been working through a problem an arrived at x^3-3x+1. I can solve this using the simultaneous equation solver of my calculator but this gives me decimal answers. Is there a way to get this exactly? Anybody with mathematica handy care to lend me a hand?

    Thanks for any help,

    Wes
     
  2. Kobushi macrumors 6502a

    Kobushi

    Joined:
    Jun 7, 2005
    Location:
    Right behind you.
    #2
    Heh... here's what MatLab spits out.... for what it's worth.


    Stupid cubics and their complex roots. (those are 3 different roots, and I already ran <simplify> )


    1/2*((-4+4*i*3^(1/2))^(2/3)+4)/(-4+4*i*3^(1/2))^(1/3)

    1/4*(-(-4+4*i*3^(1/2))^(2/3)-4+i*3^(1/2)*(-4+4*i*3^(1/2))^(2/3)-4*i*3^(1/2))/(-4+4*i*3^(1/2))^(1/3)

    -1/4*((-4+4*i*3^(1/2))^(2/3)+4+i*3^(1/2)*(-4+4*i*3^(1/2))^(2/3)-4*i*3^(1/2))/(-4+4*i*3^(1/2))^(1/3)
     

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