Answer: -54
Step-by-step explanation:
The maximum area of the pen is the highest area the pen can have
The maximum area is 16200 square yards
Let the dimension be x and y.
So, the perimeter is given as:

Because it has one additional fence, the perimeter is calculated as:

Make y the subject

The area is calculated as:

Substitute 

Expand

Differentiate

Set to 0

Rewrite as:

Divide both sides by 4

Substitute 90 for x in 


Hence, the maximum area is 16200 square yards
Read more about maximum areas at:
brainly.com/question/11906003
i think it would be y=18x
i do not know you answer choices or any good details
y=18x is answer