SOLUTION: A fence must be built to enclose a rectangular area of 45,000 ft^2. Fencing material costs $1 per foot for the two sides facing north and south and ​$2 per foot for the other two

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Question 1192763: A fence must be built to enclose a rectangular area of 45,000 ft^2. Fencing material costs $1 per foot for the two sides facing north and south and ​$2 per foot for the other two sides. Find the cost of the least expensive fence.
The cost of the least expensive fence is ​$___?
  
please answer the blank space with solving. Thank you
Answer by MathLover1(20850)   (Show Source): You can put this solution on YOUR website!
Let = the of rectangle in ft, = the of rectangle in ft.
A fence must be built to enclose a rectangular area of
=>
The cost of the fence is:



substitute
,

Find the first derivative with respect to
′
Find the critical value(s)
′

=>
=>

Since , then the function has the absolute minimum at .
so,
and, the cost will be:


The cost of the least expensive fence is ​$?

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