Question 758129
A = 100w - w^2
Differentiate
A' = 100 - 2w
A' = 0
     100 - 2w = 0
         - 2w = - 100
           2w = 100
            w = 50
Using a nature table.
50 feet is the maximum width
Given 200 feet of fencing
Length = 50 feet
Width = 50ft
Area = length x width
         50 x 50
         2500 ft^2
Hope this helps.
:-)