Question 122434
Let x = width
    4x-4 = length (4 cm less than 4 times the width)
since Area  = length X width

Substitute values... to eqtn of Area

31 = x(4x-4)
31 = 4x2 - 4x
0 = 4x2 - 4x - 31
Using quadratic formula,{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}
You'll get 2 values 1 positive and 1 negative...
The correct answer is the positive answer which is 3.328cm (rounded off)