document.write( "Question 1097035: Marlon wants to fence a rectangular area that has one side bordered by an irrigation. If he has 80 m of fencing materials, what are the dimensions and the maximum area he can enclose? \n" ); document.write( "
Algebra.Com's Answer #711536 by Fombitz(32388)\"\" \"About 
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Let the length along be irrigation side by Y and the width be X.
\n" ); document.write( "The fence would then have a perimeter of \"P=2X%2BY=80\"
\n" ); document.write( "The area enclosed would be \"A=XY\"
\n" ); document.write( "From the perimeter equation,
\n" ); document.write( "\"Y=80-2X\"
\n" ); document.write( "Substituting into the area equation,
\n" ); document.write( "\"A=X%2880-2X%29=-2X%5E2%2B80X\"
\n" ); document.write( "To find the maximum area, convert to vertex form,
\n" ); document.write( "\"A%28X%29=-2%28X%5E2-40X%29\"
\n" ); document.write( "\"A%28X%29=-2%28X%5E2-40X%2B400%29%2B800\"
\n" ); document.write( "\"A%28X%29=-2%28X-20%29%5E2%2B800\"
\n" ); document.write( "So the maximum area of \"800\"\"m%5E2\" occurs when \"X=20\"\"m\",
\n" ); document.write( "So then,
\n" ); document.write( "\"Y=80-2%2820%29\"
\n" ); document.write( "\"Y=80-40\"
\n" ); document.write( "\"Y=40\"\"m\"
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