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Math Help - Differentiation help.

  1. #1
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    Unhappy Differentiation help.

    Hey right so I'm currently studying Pure Maths and I'm getting a bit confused on differentiation :/
    Just wondering how would I differentiate 16√x and 32/x thanks!
    Last edited by mr fantastic; December 18th 2011 at 07:09 PM. Reason: Title.
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  2. #2
    Super Member ILikeSerena's Avatar
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    Re: Differentiation help?!??

    Welcome to MHF, JodieR11!

    Did you know the following?

    16 \sqrt{x} = 16 x^{1 \over 2}

    {32 \over x} = 32 x^{-1}

    Perhaps you know how to differentiate those?
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  3. #3
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    Re: Differentiation help?!??

    Nope, I still don't :s I really don't understand and get easily confused! :/ how do you differentiate that? and thank you!
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  4. #4
    Super Member ILikeSerena's Avatar
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    Re: Differentiation help?!??

    Okay, then the next hint is that the derivative of:
    c x^n
    is
    c n x^{n-1}

    where n and c are arbitrary constants.

    So for instance the derivative of
    2x^3
    is
    2 \cdot 3 x^2


    Can you apply this?
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  5. #5
    Super Member TheChaz's Avatar
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    Re: Differentiation help?!??

    Jodie, it sounds like you don't know how to differentiate anything...

    Maybe you could type out an example of a derivative that you DO know, so we can help you from there.

    The power rule of derivatives is arguably the first rule that you would learn, so if you can't do that...
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  6. #6
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    Re: Differentiation help?!??

    I know that you bring the power to the front and then less one. Like, 2x^4 is 8x^3 so the basics! But when it gets to harder things like square roots, negative powers and fractions I know nothing Could you please link me to a site or rules or anything helpful? I have an exam in January and I'm trying to revise now :s thanks for replying and giving help, I'm new to this site and I really think it's helping
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  7. #7
    Super Member ILikeSerena's Avatar
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    Re: Differentiation help?!??

    Well, can you apply this to 32x^{-1}?

    And if you like my posts, please press the Thanks button in the left bottom of my posts.
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  8. #8
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    Re: Differentiation help?!??

    so does it just go -31^-2? I have a question which says.....
    The curve C has equation y=16√x + 32/x + 2
    a. Find the value of dy/dx when x=4
    b. Find the equation of the normal to C at the point where x=4

    I can find the equation of the normal when I have the coordinates or one coordinate and I have to find the other and only is y=3x^2 - 8x +7 something like that!
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  9. #9
    Super Member ILikeSerena's Avatar
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    Re: Differentiation help?!??

    Close, but it should be:

    32 \cdot -1 \cdot x^{-2} = -32 x^{-2} = -{32 \over x^2}.

    We'll get to your question in a sec.
    Let's first finish your derivative.

    Can you deduce what the derivative of 16 x^{1 \over 2} is?
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  10. #10
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    Re: Differentiation help?!??

    Is it 8^-1/2?
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  11. #11
    Super Member ILikeSerena's Avatar
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    Re: Differentiation help?!??

    Close, but you seem to have lost an x (just like before)...
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  12. #12
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    Re: Differentiation help?!??

    ooops yeah, I know there is supposed to be an X there! so is that right?
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  13. #13
    Super Member ILikeSerena's Avatar
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    Re: Differentiation help?!??

    Erm... is what right?

    If you think you have it, then what is the dy/dx in your problem?
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  14. #14
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    Re: Differentiation help?!??

    8x^-1/2 - 32/x^2?
    But how to I sub in the 4 in my problem or when it says when x=4
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  15. #15
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    Re: Differentiation help?!??

    does the -32/x^2 turn to -2??
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