SOLUTION: Beth has 3,000 feet of fencing available to enclose a rectangular field. One side of the field lies along a river, so only three sides require fencing. (a) Express the area A of t

Algebra ->  Customizable Word Problem Solvers  -> Geometry -> SOLUTION: Beth has 3,000 feet of fencing available to enclose a rectangular field. One side of the field lies along a river, so only three sides require fencing. (a) Express the area A of t      Log On

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Question 59545: Beth has 3,000 feet of fencing available to enclose a rectangular field. One side of the field lies along a river, so only three sides require fencing.
(a) Express the area A of the rectangle as a function of x, where x is the length of the side parallel to the river.
(b) Graph A = A(x) using a graphing utility. For what value of x is the area largest?
A wire of length x is bent into the shape of a circle.
(a) Express the circumberence of the circle as a function of x.
(b) Express the area of the circle as a function of x.

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
If the side parallel to the river is x,
the remaining 2 sides are equal and each
equals %283000+-+x%29%2F2
A+=+x%2A%283000+-+x%29+%2F+2
A+=+-%281%2F2%29x%5E2+%2B+1500x

From the graph, it looks like A is maximum when x = 1500
A would be (1500)^2 / 2 then or 1,125,000 sqare feet
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C+=+x answer
to find the area in terms of x, first find the area in terms of the
circumference
A+=+pi%2Ar%5E2 where r is the radius
C+=+2%2Api%2Ar
C+=+x ,so
x+=+2%2Api%2Ar
Another way to express A is
A+=+pi%2Ar%2Ar
multiply both sides by 2
2A+=+2%2Api%2Ar%2Ar
2A+=+x%2Ar
but
r+=+x+%2F+%282%2Api%29
so
2A+=+x%2A%28x+%2F+%282%2Api%29%29
A+=+x%5E2+%2F+%284%2Api%29 answer