April 24, 2015

Homework Help: Optimization (Math)

Posted by Tommy on Tuesday, November 1, 2011 at 12:08pm.

The mayor of a village wants to build a library of which the windows have a shape of a rectangle on top of a square. The total perimeter of each window is of P meters and varies depending on each windows size. Find the dimensions of the windows in terms of P, that maximizes the area of all the windows.

Because I can't draw on here, the perimeter I have is

6x + 2y = P

(3x for each of the squares sides, because the rectangle covers the last one, 2y for each of the rectangles sides, and the last 3x are the rectangles length, x being half the length of the rectangle, so 2x on top of the rectangle and 1x at the bottom, because the other x is the junction between the square and the rectangle.)

| |-------|

For the area, I found:

p = 6x +2y
y = (P-6x)/2


A(x) = x^2 + 2x((P-6x)/2)

now, I know I have to derive A(x)
but what I'm not sure is if the derivative of P will be 0, or do I simply leave P as it is?

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