Answer:
Part 1 : The area in terms of side length = 
Area of square in terms of perimeter P : 
Part 2: A simple equation to find the least amount of fencing necessary for a playground with an area of 256 square yards : 
Step-by-step explanation:
Part 1 : For any given perimeter P, the rectangle that encloses the greatest area is a square. . Write an equation for the area, A, in terms of the perimeter P, and the side length x.
Solution :
We are given that the rectangle that encloses the greatest area is a square.
Let the side of the square be x
Let perimeter be P
So, perimeter of square'P' = 
So,
Area of square : 
Thus the area in terms of side length = 
Now to find area in terms of perimeter :
Since perimeter 

Now, Area of square : 
So,Area of square in terms of perimeter P : 
Part 2: Use the equation from Part I to result to write a simple equation to find the least amount of fencing necessary for a playground with an area of 256 square yards.
Since we have the equation of area in terms of perimeter :

Note: Perimeter tells the amount of fencing

Thus a simple equation to find the least amount of fencing necessary for a playground with an area of 256 square yards : 