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Homework Help: How to the derivative of this?

  1. Nov 5, 2011 #1
    1. How to take the derivative of this? i know how to derive this but i don't get what it means by when x=3
    d/dx=((x-4)^3)) when x = 3

    can you please work out a similar problem for me so i can follow the steps?

    Thank you for your help, kind regards.
  2. jcsd
  3. Nov 5, 2011 #2


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    Homework Helper

    The derivative of a function f(x) is the "slope" function. You plug in a value, call it a, into the derivative and this will tell you the slope of f(x). For instance:

    f(x) = x2
    f'(x) = 2x

    Let's say I want to find the slope of f(x) at x = 2, so we look at f'(2), so f'(2) = 2*2 = 4.
  4. Nov 5, 2011 #3
    thank you very much. i can do it now.
  5. Nov 5, 2011 #4


    Staff: Mentor

    Your notation needs some work as well.
    d/dx is the derivative operator. It's not a number. It makes about as much sense to write d/dx = (x - 4)3 as it does to write √ = 7. In this nonsense equation, a natural question would be, the square root of what equals 7.

    In what you wrote, the question would be, the derivative of what equals (x - 4)3?

    Also, in English we don't "derive" something when we take the derivative - we say that we "differentiate" a function to get its derivative. Must seem weird, but that's the common usage.
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