A farmer wants to fence an area of 24 million square feet in a rectangular field and then divide it in half with a fence parallel to one of the sides of the rectangle. What should the lengths of the sides of the rectangular field be so as to minimize the cost of the fence?
smaller value? and larger value?

Question

campbell_st · Answer

well you need to look at what you know

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you know the area 

24 000 000 = lw

and the perimeter will be 

P = 2l + 2w

you need to rewrite the area equation and make w the subject. 

Then substitute it into the perimeter equation so the you have a an equation in 1 unknown. 

next differentiate the perimeter equation with respect to l to find the stationary point