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Beth has 3000 feet of fencing available to enclose a rectangular field.

(a) Express the area A of the rectangle as a function of x, where x is the length of the rectangle.

(b) For what value of x is the area largest?

(c) What is the maximum area?

Short Answer

Expert verified

(a) The area A of the rectangle as a function of x is A(x)=-x2+1500x

(b) For the area to be the largest x should be 750

(c) Maximum area is 562500

Step by step solution

01

Part (a) Step 1. Given information

Beth has 3000 feet of fencing available to enclose a rectangular field

02

Part (a) of Step 2. Area A of the rectangle as a function of x. 

Beth has 3000 feet of fencing

Let, x be the length and w be the width

Therefore

2x+2w=3000x+w=1500w=1500-x

The area of the rectangle is A=xw

Substitute the value of w in the equation of the area.

localid="1649807567794" A=x1500-x

A as a function of x will be.

localid="1649807877743" A=-x2+1500x

03

Part (b) of Step 1.  value of x .

The value of the area is the largest in the vertex.

A=-x2-2·750·x+7502-7502=-x2-2·750·x+7502+7502=-x-7502+7502

So, the area is the largest when x=750.

04

Part (c) of Step 1.  Maximum area 

Substitute x=750 in the equation A=-x2+1500x

A(750)=-7502+1500·750A(750)=562500

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