SOLUTION: one hundred feet of fencing is to be used to enclose a rectangular garden that abuts to a barn. No fencing is needed along the barn. What is the largest possible area that can be

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Question 332820: one hundred feet of fencing is to be used to enclose a rectangular garden that abuts to a barn. No fencing is needed along the barn. What is the largest possible area that can be enclosed?
Answer by jrfrunner(365)   (Show Source): You can put this solution on YOUR website!
Perimeter of the rectangular garden = 2*W+L (one side is covered by the barn)
The area of the garden = L*W
==
so we know we have a total of 100 feet of fencing
therefore,
solve this for L:
substitute the L into the area formula : A=L*W


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To find the minimum or maximum area, take the derivative and set to 0
why? because a min or max will occur when the slope is 0, flat part of the function.
--
dA/dW = 100 -4*w =0, solve for W
W=100/4=25 is this a min or max? if second derivative at w=25 is negative then its a maximum, why?
because the second derivative relates to the curvature of the function, so if its negative its curving downward
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d^2A/dW^2= -4 thus function is curving downward, W=25 is a maximum
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now W=25 means that L=100-2*W=50
therefore
max Area=L*W=25*50=1250 ft^2

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