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Math Help - Basic question - derivatives

  1. #1
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    Question Basic question - derivatives

    Hi,

    I'm really new to this, just trying to get my head around things.

    I've been given the question: 1/sqrt(x) + 3x - x (I've attached a clearer jpeg version)

    I'm using the formula: y' = b * ax ^b-1

    I am getting the answer '3', through the following working out, however this does not correspond to the answer given by online derivative calculators.

    --------------------------------

    #1:

    1/sqrt(x) + 3x - x

    #2:

    1/sqrt(x^1) + 3x^1 - x^1

    #3:

    1/sqrt(1x^1-1) + 1(3x^1-1) - 1x^1-1

    #4:

    1/sqrt(1x^0) + 1(3x^0) - 1x^0

    #5:

    1/sqrt(1) + 3 - 1

    #6:

    1 + 3 -1 = Ans 3


    ------------------------------------

    Can anyone help me with this? Just need to know where or if I'm going wrong.

    Thanks.
    Daniel.
    Attached Thumbnails Attached Thumbnails Basic question - derivatives-question.jpg  
    Last edited by mr fantastic; April 17th 2010 at 08:39 PM.
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  2. #2
    MHF Contributor
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    Quote Originally Posted by ashleysmithd View Post
    Hi,

    I'm really new to this, just trying to get my head around things.

    I've been given the question: 1/sqrt(x) + 3x - x (I've attached a clearer jpeg version)

    I'm using the formula: y' = b * ax ^b-1

    I am getting the answer '3', through the following working out, however this does not correspond to the answer given by online derivative calculators.

    --------------------------------

    #1:

    1/sqrt(x) + 3x - x

    #2:

    1/sqrt(x^1) + 3x^1 - x^1

    #3:

    1/sqrt(1x^1-1) + 1(3x^1-1) - 1x^1-1

    #4:

    1/sqrt(1x^0) + 1(3x^0) - 1x^0

    #5:

    1/sqrt(1) + 3 - 1

    #6:

    1 + 3 -1 = Ans 3


    ------------------------------------

    Can anyone help me with this? Just need to know where or if I'm going wrong.

    Thanks.
    Daniel.

    \frac{1}{\sqrt{x}} + 3x - x

    \frac{1}{\sqrt{x}} + 2x

    x^{-\frac{1}{2}} + 2x<br />

    \frac{d}{dx}\left(x^{-\frac{1}{2}} + 2x\right)

    -\frac{1}{2} x^{-\frac{3}{2}} + 2

    -\frac{1}{2x\sqrt{x}} + 2


    ... in future, please post calculus questions in the calculus section.
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