We are going to name variables to solve the problem:
x = length
(x-8) = width
The area of the rectangle by definition is:
A = (x) * (x-8) = 84
Rewriting:
(x) * (x-8) = 84
x ^ 2-8x-84 = 0
Solving the polynomial:
(x-14) * (x + 6) = 0
x = 14
x = -6
We need the values x> 0
Thus,
x = 14 (length)
(14-8) = 6 (wide)
Answer:
the dimensions of a rectangle are
length = 14 mi
wide = 6 mi
