perimeter = 2 x + 2 y
cost = c = 14 x + 4 y = 15400
or
7 x + 2 y = 7700
y = -3.5 x + 3850
A = x y = x(-3.5 x + 3850)
= -3.5 x^2 + 3850 x
dA/dx = -7x +3850
zero when
x = 3850/7
etc
A rectangular plot of land is to be fenced in using two kinds of fencing. Two opposite sides will use heavy-duty fencing selling for $7 a foot, while the remaining two sides will use standard fencing selling for $2 a foot. What are the dimensions of the rectangular plot of greatest area that can be fenced in at a cost of $15,400?
1 answer
2 answers