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Math Help - Finding critical numbers

  1. #1
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    Finding critical numbers

    I am stuck on a question for my calc h.w

    it reads to find the critical numbers of x^-2 ln x

    When I took the derivative I got -2x^-3 lnx + x^-2 *1/x

    I simplified and set it equal to zero. the critical numbers i got were 0 and e^1/2 however the question says I'm wrong
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  2. #2
    MHF Contributor MarkFL's Avatar
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    Re: Finding critical numbers

    What is the domain of the function?
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  3. #3
    Senior Member MaxJasper's Avatar
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    Lightbulb Re: Finding critical numbers

    Quote Originally Posted by neontiger94 View Post
    it reads to find the critical numbers of x^-2 ln x
    When I took the derivative I got -2x^-3 lnx + x^-2 *1/x
    I simplified and set it equal to zero. the critical numbers i got were 0 and e^1/2 however the question says I'm wrong
    This might apply:

    Attached Thumbnails Attached Thumbnails Finding critical numbers-critical-numbers.png  
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  4. #4
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    Re: Finding critical numbers

    sorry thats not correct it's x^-2 * lnx
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    MHF Contributor MarkFL's Avatar
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    Re: Finding critical numbers

    What is the domain of that function?
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  6. #6
    Senior Member MaxJasper's Avatar
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    Lightbulb Re: Finding critical numbers

    Attached Thumbnails Attached Thumbnails Finding critical numbers-critical-numbers2.png  
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  7. #7
    Junior Member alane1994's Avatar
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    Re: Finding critical numbers

    To find critical points, you find the derivative. Then you set the derivative equal to zero. You then solve for x. Those are then candidates for local maxima or minima.
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