Question 929542
{{{A=L*W=84}}}
{{{P=2(L+W)=40}}}
{{{L+W=20}}}
Substituting,
{{{L=84/W}}}
into the perimeter equation,
{{{84/W+W=20}}}
{{{84+W^2=20W}}}
{{{W^2-20W+84=0}}}
{{{(W-14)(W-6)=0}}}
Two solutions:
{{{W-14=0}}}
{{{W=14}}}
Then,
{{{L=84/14}}}
{{{L=6}}}
and
{{{W-6=0}}}
{{{W=6}}}
and
{{{L=84/6}}}
{{{L=14}}}