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Thread: Please help

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    Please help

    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

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    Re: Please help

    The hieght is root 125/3 too, try subbing it in, both equations they seem right

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    Re: Please help

    Which formula h=125x^2/2x???

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    Re: Please help


    THis is from the previous post, If u sub in the values you should get the same answer
    EG) Let A = sqrt125/3 (just repetitive introducing pronumeral as a value holder)

    A^3=V(formula) = (125A-A^3)/2
    Where A is x

    Also try seeing the y = (125-x^2)/(2x), if u sub in x = A, u will get y=x

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