Question

a farmer wants to make a rectangular enclosure using a wall as one side and 120 m of fencing for the other three sides.
a) express the area in terms of x and state the domain of the area function
b)find the value of x that gives the greatest area.


my teacher didn't explain how to do this so im not sure, please help!

Answer 1

perimeter= 2s + l
120=2s + l

area= sl= s(120-2s)

Take the deriviative of area with respect to s, set to zero, and find s,l.

Answer 2

Oooppps. If you are in precal, you may not know derivative yet. In that case, graph A vs s, look for the max A, read where s is, then solve for l knowing s.

Answer 3

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