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Thread: Please help

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    Please help

    A square based rectangular prism is to have surface area of 250cm^2 and volume Vcm^3.
    I) show V =( 125x-x^3)/2

    I get this part but I don’t get part II

    II) find the dimensions for maximum volume.

    I got the derivative and let it equal zero and got x = root 125/3. Then I got V’’ and found that it is less than zero and therefore a max but how do I get the dimensions. I know the length and width is just root 125/3 but what is the height

  2. #2
    Traveller from the North fan96's Avatar
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    Re: Please help

    Let the dimensions be .



    Since ,



    HSC 2018 - [English Adv.] • [Maths Ext. 1] • [Maths Ext. 2] • [Chemistry] • [Software Design and Development]

    1(3√3) t2 dt cos(3π/9) = log(3√e) | Integral t2 dt, From 1 to the cube root of 3. Times the cosine, of three pi over nine, Equals log of the cube root of e.

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