Problema Solution
A farmer wants to use a stream as one side of his rectangular pen that he is building. The other three sides will use 800 feet of fencing. You find the dimensions that make the area of the rectangular pen the greatest.
Answer provided by our tutors
2x + y = 800, y = 800 - 2x
maximize xy
x(800-2x) = 800x - 2x^2
f' = 800 - 4x = 0
4x = 800
x = 200
So pick dimensions 200 x 400
(200, 400, 200) for the 3 sides of the fence