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Math Help - rolle's theorem

  1. #1
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    rolle's theorem

    Can someone explain indepth how to get the solution to this question.

    Show that the equation (x^4)+4x+c=0 has at most two real roots.

    please and thanks.
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  2. #2
    MHF Contributor Mathstud28's Avatar
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    Quote Originally Posted by johntuan View Post
    Can someone explain indepth how to get the solution to this question.

    Show that the equation (x^4)+4x+c=0 has at most two real roots.

    please and thanks.
    Use Demoivre's sign change theorem. If c<0 then there is one sign change and if you sub -x for x you get one sign change...so if c<0 you have one positive real root and one negative...if c>0 you only have one real negative root
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