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Math Help - Finding Intervals of increase and decrease

  1. #1
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    Finding Intervals of increase and decrease

    The Function:

    f(x)=x^3-x^2+4x-3

    Find the first and second derivative:

    f'(x)=3x^2-2x+4
    f''(x)=6x-2

    I'm stuck on finding f'(x)=0, I have tried many ways, none have worked.

    I have tried using the quadratic formula which does not work, because -2^2-(4(3)(4)) is a negative and I cannot square root it.


    I don't know how to delete posts, skeeter solved this question about a month ago.

    http://www.mathhelpforum.com/math-he...-function.html
    Last edited by Butum; April 6th 2010 at 09:31 AM.
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  2. #2
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    Quote Originally Posted by Butum View Post
    The Function:

    f(x)=x^3-x^2+4x-3

    Find the first and second derivative:

    f'(x)=3x^2-2x+4
    f''(x)=6x-2

    I'm stuck on finding f'(x)=0, I have tried many ways, none have worked.

    I have tried using the quadratic formula which does not work, because -2^2-(4(3)(4)) is a negative and I cannot square root it.


    Of course the quadratic formula works and works marvelously! That the quadratic's discriminant b^2-4ac is negative means there are no real roots and thus the function's derivative doesn't vanish at any real number and thus there are no extreme points.

    Tonio



    I don't know how to delete posts, skeeter solved this question about a month ago.

    http://www.mathhelpforum.com/math-he...-function.html
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  3. #3
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    I never considered looking at it that way, thanks
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