document.write( "Question 36209: Please help! Submitted question earlier didn't get a response.\r
\n" ); document.write( "\n" ); document.write( "4) Amanda has 400 feet of lumber to frame a rectangular patio (the perimeter of a rectangle is 2 times length plus 2 times width). She wants to maximize the area of her patio (area of a rectangle is length times width). What should the dimensions of the patio be, and show how the maximum area of the patio is calculated from the algebraic equation.\r
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Algebra.Com's Answer #22181 by Prithwis(166)\"\" \"About 
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Let the length of the rectangular patio be x ft
\n" ); document.write( "Perimeter of the rectangular patio = 400 ft
\n" ); document.write( "The width of the rectangular patio would be 1/2(400-2x) = 200-x
\n" ); document.write( "Area = Length * Width = x(200-x)
\n" ); document.write( "We need to maximize f(x) = x(200-x) to achieve the goal of the problem.
\n" ); document.write( "f(x) is quadratic function for Area, which represents a parabola opening downward (because the co-efficient of x^2 is negative).
\n" ); document.write( "Maximum of f(x) is reached at the vertex (because it opens downward)
\n" ); document.write( "x-Coordinate of the vertex = -b/2a (for ax^2+bx+c);
\n" ); document.write( "f(x) = -x^2+200x; So, a = -1, b=200, c=0
\n" ); document.write( "(-b/2a) = 100;
\n" ); document.write( "So, maximum area can be obtained if the length is 100 feet;
\n" ); document.write( "The width will be 1/2(400-200) = 100 feet;
\n" ); document.write( "Answer - Dimension of the patio for maximum area will be 100 feet X 100 feet\r
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