SOLUTION: Suppose a farmer has 1000m of fencing to enclose a rectangular field. What is the largest area that the farmer can enclose?

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Question 581762: Suppose a farmer has 1000m of fencing to enclose a rectangular
field. What is the largest area that the farmer can enclose?

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The Perimeter is:
+P+=+2W+%2B+2L+
+1000+=+2W+%2B+2L+
+500+=+W+%2B+L+
+L+=+500+-+W+
-------------------
The Area is:
+A+=+W%2AL+
+A+=+W%2A%28+500+-+W+%29+
+A+=+-W%5E2+%2B+500W+
--------------------
First of all, when the coefficient of the
squared term is negative, then there is a maximum
and not a minimum.
When the equation is in the form
+y+=+ax%5E2+%2B+ba+%2B+c+, the max or min is
always at +x+=+-b%2F%282a%29+, or, in this case,
+W%5Bmax%5D+=+-500%2F%282%2A%28-1%29%29+
+W%5Bmax%5D+=+250+
and I know that
+L+=+500+-+W+
+L%5Bmax%5D+=+500+-+250+
+L%5Bmax%5D+=+250+
The largest area that the farmer can enclose
is +250%2A250+ = 62,500 ft2
-------------------------------
I can prove this by changing the dimensions
slightly, but still keeping the same Perimeter
+249%2A251+ = 62,499 ft2
+248%2A252+ = 62,496 ft2 ( even less )