2 w + L = 40 so L = 40-2w
A = w L = w (40-2w)
-2 w^2 + 40 w = A
w^2 - 20 w = -A/2
w - 20 + 100 = -(1/2)(A-200)
(w - 10)^2 = -(1/2)(A-200)
w = 10, L = 20, A = 200
Andy plans to build a rectangular dog pen in his backyard. A portion of the back wall of his house will serve as one side of the dog pen. If the perimeter of the dog pen must be 40 feet, which of the following widths will result in the maximum area?
A. 6 ft
B. 8 ft
C. 10 ft
D. 12 ft
1 answer
1 answer