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Homework Help: Differntiate the function

  1. Jun 2, 2010 #1
    ok just want a check of my work before i send it :)

    differntiate the function;
    f(x)=[tex]\frac{x(20-x)}{36}[/tex]

    so,
    f'(x)=[tex]\frac{(20x-x^2)}{36}[/tex]

    f'(x)=[tex]\frac{(20-2x)}{36}[/tex]

    f'(x)=[tex]\frac{(10-2x)}{18}[/tex]

    Then....use the composite rule and your answer above to differntiate the function
    g(x)=ex(20-x)/36

    g'(x)=f'(x)*ef(x)

    so,
    g'(x)=[tex]\frac{10-2x)}{18}[/tex]*g(x)=ex(20-x)/36

    is this correct?

    is this correct
     
  2. jcsd
  3. Jun 2, 2010 #2

    Mark44

    Staff: Mentor

    Re: differentiation

    Above - This is not f'(x). All you have done is expand the numerator on the right. This should be f(x) = ...
    Above - Now you have taken the derivative
    Above - now you have an error. 20 - 2x != 2(10 - 2x).
    Where f(x) = (1/36)(x(20 - x)). The derivative below is incorrect. To fix it, replace f'(x) and f(x) where they appear.
     
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