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Thread: (fog)(x)

  1. #1
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    (fog)(x)

    (fog)(x) =x2 + x. If g(2) = 4 and g(2) = 5 , find f (4). Thank you.
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  2. #2
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    Re: (fog)(x)

    $f[g(x)]=x^2+x$

    derivative of a composite function requires use of the chain rule ...

    $f’[g(x)] \cdot g’(x) = 2x+1$

    $f’[g(2)] \cdot g’(2) = 2(2)+1$

    $f’(4) \cdot 5 = 5 \implies f’(4)=1$
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  3. #3
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    Re: (fog)(x)

    Thanks a lot.
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