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David has available 240 yards of fencing and wishes to enclose a rectangular area.
(a) Express the area A of the rectangle as a function of the width W of the rectangle.
(b) For what value of W is the area largest?
(c) What is the maximum area?

Respuesta :

Answer:

Below in bold.

Step-by-step explanation:

Perimeter = 2*width + 2*length

So

240 = 2w + 2l

120 = w + l

l = 120 - w

(a) Area = w*l

Substituting for l:

A = w(120 - w)

A = 120w - w^2

(b)

Finding the derivative:

A = 120w - w^2

A' = 120 - 2w

For a maximum area A' = 0, so:

120 - 2w = 0

2w = 120

w = 60 yards for maximum area.

(c)

Maximum area

= 120*60 - 60^2

= 3600 yd^2.

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