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Math Help - Finding x (this is really beyond me i think)???

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    Finding x (this is really beyond me i think)???

    This set of questions is really perplexing me!!!!

    find f '(x) given that

    f (x) = 2x^3 + 6x^2 - (cubed root of x)

    f (x) = x^2 e^(-3x)

    These really phase me a bit, any advice much appreciated.
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    Quote Originally Posted by bobchiba View Post
    This set of questions is really perplexing me!!!!

    find f '(x) given that

    f (x) = 2x^3 + 6x^2 - (cubed root of x)

    f (x) = x^2 e^(-3x)

    These really phase me a bit, any advice much appreciated.
    What's the problem with the first one? It's just the power rule:
    d/dx(ax^n) = a*n*x^{n-1}

    So:
    f(x) = 2x^3 + 6x^2 - x^{1/3}

    f'(x) = 6x + 12x - (1/3)x^{-2/3}

    Use the product rule:
    h(x) = f(x)*g(x) ==> h'(x) = f'(x)*g(x) + f(x)*g'(x)

    So for
    f(x) = x^2 e^{-3x}

    f'(x) = 2x*e^{-3x} + x^2 * (-3)e^{-3x} = 2xe^{-3x} - 3x^2e^{-3x}

    -Dan
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