document.write( "Question 37629: A farmer has $3600 to spend on fencing for three adjoining rectuangular pastures, all with the same dimensions. a local contracting company tells the farmer that they can build the fence for $6.25/m. What is the largest total area that the farmer can have fenced for that price? \n" ); document.write( "
Algebra.Com's Answer #23236 by josmiceli(19441)\"\" \"About 
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the fields would look like 3 adjoining rectangles
\n" ); document.write( "with $3600 to spend and and a cost of $6.25/m, the farmer can
\n" ); document.write( "afford 3600/6.25 = 576 m of fence
\n" ); document.write( "He needs 4 north-south lengths and 2 east-west lengths (for example)
\n" ); document.write( "in order to enclose 3 rectangular fields
\n" ); document.write( "All these lengths will add up to 576 m.
\n" ); document.write( "\"2x+%2B+4y+=+576\"
\n" ); document.write( "The area enclosed is x times y
\n" ); document.write( "\"A+=+xy\"
\n" ); document.write( "solve for y in the 1st equation
\n" ); document.write( "\"4y+=+576+-+2x\"
\n" ); document.write( "\"y+=+144+-+x%2F2\"
\n" ); document.write( "substitute this in equation 2
\n" ); document.write( "\"A+=+x%28144+-+x%2F2%29\"
\n" ); document.write( "\"A+=+-x%5E2%2F2+%2B+144x\"
\n" ); document.write( "graph the equation
\n" ); document.write( "\"+graph%28+300%2C+500%2C+-50%2C+300%2C+-500%2C+12000%2C+-x%5E2%2F2+%2B+144%2Ax%29+\"
\n" ); document.write( "I'll guess the x value where the graph is a max is 144
\n" ); document.write( "\"A+=+-x%5E2%2F2+%2B+144x\"
\n" ); document.write( "\"A+=+-%28144%29%5E2%2F2+%2B+144%2A%28144%29\"
\n" ); document.write( "factor out 144^2
\n" ); document.write( "\"A+=+144%5E2%2A%281+-+1%2F2%29\"
\n" ); document.write( "\"A+=+144%5E2+%2F+2\"
\n" ); document.write( "\"A+=+20736%2F2\"
\n" ); document.write( "\"A+=+10368\"
\n" ); document.write( "The way to test this is to increase 144 a little, test it in the equation
\n" ); document.write( "then decrease 144 a little and test it in the equation
\n" ); document.write( "\"A+=+-%28143%29%5E2%2F2+%2B+144%2A%28143%29\"
\n" ); document.write( "\"A+=+10367.5\"
\n" ); document.write( "\"A+=+-%28145%29%5E2%2F2+%2B+144%2A%28145%29\"
\n" ); document.write( "\"A+=+10367.5\"
\n" ); document.write( "since the area is a little bit less than 10368 on either side
\n" ); document.write( "of x = 144, then this is the max.
\n" ); document.write( "The largest Area that can be enclosed is 10368
\n" ); document.write( "----------------------------
\n" ); document.write( "check
\n" ); document.write( "If x = 144, find y
\n" ); document.write( "xy = 10368
\n" ); document.write( "y = 10368/144
\n" ); document.write( "y = 72
\n" ); document.write( "\"2x+%2B+4y+=+576\"
\n" ); document.write( "\"2%2A144+%2B+4%2A72+=+576\"
\n" ); document.write( "\"288+%2B+288+=+576\"
\n" ); document.write( "\"576+=+576\"
\n" ); document.write( "OK
\n" ); document.write( "
\n" );