A rectangular plot of farmland will be bounded on one side by a river and on the other three sides by a single-strand electric fence. With 600 m of wire at your disposal, what is the largest area you can enclose, and what are its dimensions?
2x+y=400
A=xy area of farmland
y=400-2x
A=400x-2x^2
A'(x)= 400 -4x derivative of area with respect to x
0=400-4x find out where f ' equals 0
4x=400
x=100
A'(x)= 400 -4x
A''(x)= -4 check 2nd derivative. if negative then relative max at x=100
2x+y=400
y=200
dimensions 100x200
hope it helped
