Answer:
L(min) = 125 ft
Dimensions of the pens
biggest side x /2 = 31.225 ft
shorter side w = 20.82 ft
Step-by-step explanation:
Let call w width of the pen ( the shorter side )
Let call x the biggest side of the two pen.
The configuration we get is that we will use 3 times w + just one side of x
Then total length of fence is
L = 3*w + x (1)
And area of one pen is A = (x/2)* w and that area have to be 650 ft²
650*2 = x*w ⇒ w = 1300/x
So to get L as function of x we plugg this value in equation (1)
L(x) = 3* 1300/x + x
Taking derivatives on both sides of the equation
L´(x) = -3900/x² + 1
L´(x) = 0 ⇒ x² = 3900 ⇒ x = 62.45 ft
and w = 1300/x w = 20.82 ft
And the least amount of fence is
L(min) = 3* 20.82 + 62,45
L(min) = 62.45 + 62.45
L(min) = 125 ft
