Calculus
posted by Robin .
A rancher wants to make a rectangular pen to house her animals. She will divide it up with 3 fences down the middle parallel to one side. If she has 14000 ft of fencing to work with, what are the dimensions of the pen of greatest area?
Width =
Length =
What is the greatest area pen that the rancher can make?
Area =

2x+5y=14000
a = xy = x(140002x)/5
da/dx = 2800  4x/5
da/dx=0 when x = 3500
so, the pen is 3500x1400