Question 143143
The area of a rectangle is given by length times width:  {{{A=LW}}}


For this rectangle: {{{L = 2W -4}}}, so the area is then {{{A=(2W-4)W}}}, but this is equal to {{{720*m^2}}}, so:


{{{(2W-4)W=720}}}
{{{2W^2-4W-720=0}}}
{{{W^2-2W-360=0}}}


Solving the quadratic gives you the width which can be substituted into {{{L=2W-4}}} to calculate the length.


You can do your own arithmetic for part B.  Hint:  The quadratic factors quite neatly, but one of the roots will be negative.  You can exclude that root since you are looking for a positive measure of length.