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Homework Help: AP Calc - Find a Derivative Formula

  1. Oct 10, 2009 #1
    1. The problem statement, all variables and given/known data

    If y = f(u) and u = g(x), where f and g possess third derivatives, find a formula for _LARGE__fracd3ydx3.gif similar to the one below:

    2. Relevant equations


    3. The attempt at a solution

    Ok, so I am basically completely lost on this one... because I came up with a solution for d^3y/d^3x, but not the way they want it which is d^3y/dx^3. I don't get how it can be the third derivative of y with respect to x cubed.

    Perhaps I am making it more confusing, but can someone please clarify/explain?

  2. jcsd
  3. Oct 10, 2009 #2


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    It's not the third derivative with respect to x^3. It's just the third derivative with respect to x that they want. That's just sort of a funkyness about the d/d notation.
    [tex]\frac{d^3 y}{dx^3}[/tex]
    just means the third derivative. Nothing to do with x cubed. It's just the way they write it.
    Last edited: Oct 10, 2009
  4. Oct 10, 2009 #3
    Thanks a bunch for the clarification. I think I got the right answer now. :)

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