Answer:
2500 Square meters
Explanation:
Given the garden area (as a function of its width) as:

The maximum possible area occurs when we maximize the area. To do this, we take the derivative, set it equal to zero and solve for w.
A'(w)=-2w+100
-2w+100=0
-2w=-100
w=50 meters
Since Marquise has 200 meters of fencing to build a rectangular garden,
Perimeter of the proposed garden=200 meters
Perimeter=2(l+w)
2(l+50)=200
2l+100=200
2l=200-100=100
l=50 meters
The dimensions that will yield the maximum area are therefore:
Length =50 meters
Width=50 meters
Maximum Area Possible =50 X 50 =2500 square meters.