Question

Peter has 3200 yards of fencing to enclose a rectangular area. Find the dimensions of the rectangle that maximize the enclosed area. What is the maximum​ area?

Answer 1

Answer:

$A = 640000\,yd^{2}$

Step-by-step explanation:

Expression for the rectangular area and perimeter are, respectively:

$A (x,y) = x\cdot y$

$3200\,yd = 2\cdot (x+y)$

After some algebraic manipulation, area expression can be reduce to an one-variable form:

$y = 1600 -x$

$A (x) = x\cdot (1600-x)$

The first derivative of the previous equation is:

$\frac{dA}{dx}= 1600-2\cdot x$

Let the expression be equalized to zero:

$1600-2\cdot x=0$

$x = 800$

The second derivative is:

$\frac{d^{2}A}{dx^{2}} = -2$

According to the Second Derivative Test, the critical value found in previous steps is a maximum. Then:

$y = 800$

The maximum area is:

$A = (800\,yd)\cdot (800\,yd)$

$A = 640000\,yd^{2}$

Answer 2

Answer:

74/4= 18.5

Step-by-step explanation: