Question 936218
let width be x feet
 length was 4 less than twice the width
  length  = 2*x-4
  area  = width x length
  420 = x* (2x-4)
   420 = x*2x-x*4
 {{{ 420 =2x^2-4x}}}
    move 420 to the right
 {{{0 = 2x^2-4x-420}}}
*[invoke quadratic "x", 2, -4, -420 ]
 x= 15.53 , -13.53
 but x cannot be negative
 hence  width (w) = 15.53  feet
 length (l) = 2*15.53-4
            = 31.06-4
             = 27.06 feet
length  = 27.06 feet & width  = 15.53 feet