document.write( "Question 628179: If a rectangle with length L and width W has a perimeter of 4 cm, what are the definitions of the rectangle with the largest area and what is that area? \n" ); document.write( "
Algebra.Com's Answer #395430 by josmiceli(19441)\"\" \"About 
You can put this solution on YOUR website!
The formula for perimeter is
\n" ); document.write( "\"+P+=+2L+%2B+2W+\"
\n" ); document.write( "given:
\n" ); document.write( "\"+P+=+4+\" cm
\n" ); document.write( "\"+4+=+2L+%2B+2W+\"
\n" ); document.write( "\"+2+=+L+%2B+W+\"
\n" ); document.write( "\"+W+=+2+-+L+\"
\n" ); document.write( "------------
\n" ); document.write( "The formula for area is
\n" ); document.write( "\"+A+=+W%2AL+\"
\n" ); document.write( "By substitution:
\n" ); document.write( "\"+A+=+%28+2+-+L+%29%2AL+\"
\n" ); document.write( "\"+A+=+-L%5E2+%2B+2L+\"
\n" ); document.write( "This is a parabola with \"A\" plotted on the
\n" ); document.write( "vertical axis and \"+L+\" on the horizontal.
\n" ); document.write( "The minus sign in front of \"+L%5E2+\" means
\n" ); document.write( "the parabola has a maximum, not a minimum.
\n" ); document.write( "------------------------------------
\n" ); document.write( "If the equation has the form \"+f%28L%29+=+a%2AL%5E2+%2B+b%2AL+%2B+c+\",
\n" ); document.write( "then the \"+L+\" coordinate of the maximum is at
\n" ); document.write( "\"+-b%2F%282a%29+\"
\n" ); document.write( "\"+a+=+-1+\"
\n" ); document.write( "\"+b+=+2+\"
\n" ); document.write( "\"+L%5Bmax%5D+=+-2%2F%282%2A%28-1%29%29+\"
\n" ); document.write( "\"+L%5Bmax%5D+=+1+\"
\n" ); document.write( "So, the max is at ( 1,A ) where \"+A+\" is
\n" ); document.write( "\"+A+=+-1%5E2+%2B+2%2A1+\"
\n" ); document.write( "\"+A+=+-1+%2B+2+\"
\n" ); document.write( "\"+A+=+1+\"
\n" ); document.write( "The maximum area is 1 cm2
\n" ); document.write( "and, if \"+L=1+\", then
\n" ); document.write( "\"+W+=+2+-+L+\"
\n" ); document.write( "\"+W+=+2+-+1+\"
\n" ); document.write( "\"+W+=+1+\"
\n" ); document.write( "So the maximum area is when the rectangle is a square
\n" ); document.write( "with \"+L=W=1+\"
\n" ); document.write( "
\n" ); document.write( "
\n" );