I have to find the maximum area of a rectangle that already has a 100m fence in the ground, and I am given 200m to add onto it. However, my answer doesn't make sense:
A=b x h
P=300=2b + 2h
300=2(100+x)+2h
300=200+2x+2h
h=50-x
A=b(50-x)
A=50b-xb
dA/db = 50-x
0=50-x
x=50