document.write( "Question 57121: A farmer has 4000 feet of fencing available to enclose a rectangular area and divide it into four plots. One side will extend beyond a barn that is 60 feet long. Fencing will not be needed along the barn. Let x represent the length of the side of the rectangle. Express the area A of the rectangle as a function of x. \n" ); document.write( "
Algebra.Com's Answer #38920 by ankor@dixie-net.com(22740)\"\" \"About 
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A farmer has 4000 feet of fencing available to enclose a rectangular area and divide it into four plots. One side will extend beyond a barn that is 60 feet long. Fencing will not be needed along the barn. Let x represent the length of the side of the rectangle. Express the area A of the rectangle as a function of x.\r
\n" ); document.write( "\n" ); document.write( "Let x = the length of the long side
\n" ); document.write( "Let (x-60) = the side that uses the 60' barn.
\n" ); document.write( "In order to have 4 plots, 5 width sized fences required
\n" ); document.write( ":
\n" ); document.write( "Perimeter: x + (x-60) + 5w = 4000
\n" ); document.write( " 2x - 60 + 5w = 4000
\n" ); document.write( " 2x + 5w = 4000 + 60
\n" ); document.write( " 2x + 5w = 4060
\n" ); document.write( " 5w = 4060 - 2x
\n" ); document.write( " w = (4060/5) - (2/5)x
\n" ); document.write( " w = 812 - .4x
\n" ); document.write( ":
\n" ); document.write( "Area = L*W
\n" ); document.write( ":
\n" ); document.write( "Subsitute x for L and (812-.4x) for w
\n" ); document.write( "Area = x(812-.4x)
\n" ); document.write( "A = 812x - .4x^2
\n" ); document.write( "f(x) = -.4x^2 + 812x, the area as function of x (length)
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