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Math Help - Equation of the normal line?

  1. #1
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    Equation of the normal line?

    Find the equation of the normal line to the graph of y=√ 8x at x=2.
    The part that I'm stuck at is...how do you get the derivative of y=√ 8x? The book gives me 4 / √ 8x for the derivative. How do you get that?

    I know how to do the rest, just not how to take the derivative of that type of function

    Thanks so much
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  2. #2
    Super Member Quacky's Avatar
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    Windsor, South-East England
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    Re: Equation of the normal line?

    Their notation is very messy, in my opinion.

    y=\sqrt{8x}=2\sqrt{2}\cdot x^{0.5}

    Now apply the power rule. If you prefer, you can go straight into the power rule, as we have 8^{0.5}x^{0.5} and the 8^{0.5} is just a constant. Either way, I'd avoid their notation if possible; I get an answer of \sqrt{\frac{2}{x}} which is equivalent to theirs, although I've simplified slightly.
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