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Math Help - differentiating a function...

  1. #1
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    Question differentiating a function...

    I think I have this, but want to make sure...
    Let g(x)= x^2 f(x)
    What does g'(x)=?
    Using the power rule I come up with (2x * f(x) * f'(x) )*(x^2 * f'(x))
    Is that right?
    Any help would be greatly appreciated.
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  2. #2
    Moo
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    Hello,
    Quote Originally Posted by bemidjibasser View Post
    I think I have this, but want to make sure...
    Let g(x)= x^2 f(x)
    What does g'(x)=?
    Using the power rule I come up with (2x * f(x) * f'(x) )*(x^2 * f'(x))
    Is that right?
    Any help would be greatly appreciated.
    Nope, you have to use the product rule :
    [uv]'=u'v+uv', where u=x^2 and v=f
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  3. #3
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    moo...

    could you refresh me on how to work through that?
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  4. #4
    Moo
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    Quote Originally Posted by bemidjibasser View Post
    could you refresh me on how to work through that?
    g(x)=x^2 *f(x)

    The product rule of differentiation says that
    g'(x)=[x^2]'*f(x)+x^2 *[f(x)]'=2x*f(x)+x^2*f'(x)

    Does it look clear ?
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  5. #5
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    reply

    yeah, that's what i had, right?
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  6. #6
    Moo
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    Quote Originally Posted by bemidjibasser View Post
    yeah, that's what i had, right?
    (2x * f(x) * f'(x) )*(x^2 * f'(x))
    2x*f(x)+x^2*f'(x)
    This is not the same at all
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  7. #7
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    ooops...

    I had a * not a + thanks a bunch MOO!
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