Question 933994
For a rectangle,
{{{A=L*W}}}
{{{L*W=90}}}
Length of planter needs to be three feet longer than twice its width
{{{L=3+2W}}}
Substitute into the area equation,
{{{(3+2W)W=90}}}
{{{2W^2+3W=90}}}
{{{2W^2+3W-90=0}}}
{{{(W-6)(2W+15)=0}}}
Only the positive solution makes sense here.
{{{W-6=0}}}
{{{W=6}}}
Then,
{{{L=3+2(6)}}}
{{{L=3+12}}}
{{{L=15}}}