Question 1115738
Dimensions x and y;
{{{2x+y=80}}}
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{{{A=xy}}}


{{{A(x)=x(80-2x)}}}



{{{x(80-2x)=0}}}
{{{x(40-x)=0}}}
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{{{system(Roots_Are,0,and,40)}}}


The maximum for A occurs exactly between the two roots, so maximum A is at {{{highlight_green(x=20)}}}.  This means {{{highlight_green(y=40)}}}.


This max area {{{A=20*40=highlight(800)}}}.