document.write( "Question 20126: \"7x%2B3y=pi\"
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Algebra.Com's Answer #9720 by AnlytcPhil(1806)\"\" \"About 
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7x + 3y = p
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document.write( "4x - 6y = p2\r
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document.write( "Multiply the first equation by 2 to eliminate the terms in y:
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document.write( "14x + 6y = 2p
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document.write( " 4x - 6y = p2
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document.write( "Add the two equations vertically term by term
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document.write( "18x      = 2p - p2
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document.write( "Divide both sides by 18,
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document.write( "x = (2p - p2)/18
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document.write( "or if you like you can factor p
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document.write( " out of the numeration
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document.write( "x = p(2-p)/18
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document.write( "Ordinarily we would substitute this in one of the original equations 
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document.write( "to find y.  However, when the value is troublesome to substitute in, it 
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document.write( "is much easier to start over and eliminate the other variable, x.
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document.write( "7x + 3y = p
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document.write( "4x - 6y = p2
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document.write( "We can eliminate the x terms in the first by multiplying the 
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document.write( "first equation by 4 and the second equation by -7
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document.write( " 28x + 12y = -7p
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document.write( "-28x + 42y = 7p2
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document.write( "Adding these gives
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document.write( "       54y = -7p+7p2
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document.write( "         y = (-7p+7p2)/54
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document.write( "and you may factor out -7p
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document.write( " and end up with
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document.write( "y = -7p(1-p)/54\r
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document.write( "Edwin \n" );
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