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Math Help - help find critical points/good one

  1. #1
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    help find critical points/good one

    I am working a problem on mathlab. It looks straightforward until I apply the quadratic formula and I get a negative number under a square root, which isn't allowed.

    Locate the critical points of the function f(x)=x^3+4x^2+9x+1

    the derivative is  f'=3x^2+8x+9

    Critical points are when F'=0, so I apply the quadratic formula to find the CP's.

    \frac{-(8) + or - \sqrt{8^2 - 4(3)(9)}}{2(3)}

    this will simply to
    \frac{-8+ \sqrt{-44}}{6} and \frac{-8-\sqrt{-44}}{6}
    The negative number in the sqrt doesn't make sense.
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  2. #2
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    Re: help find critical points/good one

    it does make sense ... the original function has no critical values. What does that tell you?
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    Re: help find critical points/good one

    That there is no local maxima or minima
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