precalc
posted by INEEDHELP!!! .
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!

perimeter= 2s + l
120=2s + l
area= sl= s(1202s)
Take the deriviative of area with respect to s, set to zero, and find s,l. 
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.

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