document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1127353>Question 1127353</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A rectangular yard is to be fenced in with 80 m of fence. What must the dimensions of the yard be in order to maximize the area of the field? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #743751 by </B><A HREF=/tutors/aboutme.mpl?userid=addingup><B>addingup(3677)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=addingup><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=addingup><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=743751\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Let the width be x, then the length is 80 - 2x, and the area A:<BR>\n" );
document.write( "Maximize:<BR>\n" );
document.write( "A(x) = x(80 - 2W)<BR>\n" );
document.write( "A(x) = 80x - 2x^2<BR>\n" );
document.write( "A'(x) = 80 - 4x<BR>\n" );
document.write( "find A'(x) = 0<BR>\n" );
document.write( "80 - 4x = 0<BR>\n" );
document.write( "80 = 4x<BR>\n" );
document.write( "x = 20 <BR>\n" );
document.write( "The maximum area is defined by a side of 20, this means that you will have a square yard.<BR>\n" );
document.write( "Four sides each 20 = 20 x 4 = 80, these are your 80 m. of fence<BR>\n" );
document.write( "the area is 20 x 20 = 400 m^2<BR>\n" );
document.write( " </SPAN>\n" );
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