Answer:
- x = 4
- length = 19 ft
- width = 11 ft
Explanation:
The area is given by the product of length and width.
A = LW
209 = (4x +3)(4x -5)
209 = 16x^2 -8x -15
224 = 16x^2 -8x
You could rearrange and use the quadratic formula at this point, but we elect to "complete the square".
14 = x^2 -(1/2)x
14 +1/16 = x^2 -1/2x +(1/4)^2 . . . . . add the square of half the x-coefficient
(x -0.25)^2 = 14.0625
x = 0.25 ± 3.75 . . . . . . take the square root; add 0.25
Only positive values of x are useful here, so we have
x = 4
Then the dimensions are ...
length = 4x +3 = 4(4) +3 = 19 . . . feet
width = 4x -5 = 16 -5 = 11 . . . feet