The minimum amount of fencing she can use is 126.5 ft.
An equation is an expression used to show the relationship between two or more variables and numbers.
Let x represent the length of the long side of pen and y represent the length of the small side of pen. Hence:
xy = 2000
x = 2000/y
The perimeter (P) is:
P = x + 2y
P = 2000/y + 2y
The minimum amount is at dP/dy = 0, hence:
dP / dy = 2 - 2000/y²
2 - 2000/y² = 0
2 = 2000/y²
y = 31.6 ft.
Also:
x(31.6) = 2000
x = 63.3
P = 63.3 + 2(31.6) = 126.5 ft.
The minimum amount of fencing she can use is 126.5 ft.
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