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Math Help - maximizing the area of a rectangle inscribed in a parabola

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    maximizing the area of a rectangle inscribed in a parabola

    A rectangle is inscribed with its base on the x-axis and its upper corners on the parabola y=9-[(x^2)/4] . What are the dimensions of such a rectangle with the greatest possible area?

    I found the height to be 6, but I cannot figure out the width.
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    Quote Originally Posted by yeloc View Post
    A rectangle is inscribed with its base on the x-axis and its upper corners on the parabola y=9-[(x^2)/4] . What are the dimensions of such a rectangle with the greatest possible area?

    I found the height to be 6, but I cannot figure out the width.


    A = 2xy

    A = 2x\left(9 - \frac{x^2}{4}\right)

    find \frac{dA}{dx} and determine the value of x that maximizes A.
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