The length of a rectangle is 4 inches less than twice its width. if the area of the rectangle is 70 square inches, what are its demensions

By definition, the area of a rectangle is given by:
 A = w * l
 Where,
 w: width
 l: long
 Substituting values we have:
 70 = w * (2w-4)
 Rewriting we have:
 70 = 2w ^ 2-4w
 2w ^ 2 - 4w - 70 = 0
 Solving the polynomial we have:
 w1 = -5
 w2 = 7
 We take the positive root because it is a dimension.
 w = 7 inches
 Then, the length will be:
 l = 2w-4
 l = 2 (7) -4
 l = 14-4
 l = 10 inches
 
 its demensions are:
 w = 7 inches
 l = 10 inches

Let
x-----------> the length side of rectangle
y----------> the width side of rectangle

we know that
70=x*y--------> x=70/y-----------> equation 1
x-4=2y--------> equation 2
substitute equation 1 in equation 2

[70/y]-4=2y--------> multiply by y------> 70-4y=2y²----> 2y²+4y-70=0

using a graph tool ----> to resolve the second order equation
see the attached figure

the solution is 
y=5
x=70/y--------> x=70/5=14

the answer is
the dimensions are
length=14 in
width=5 in