document.write( "Question 346673:
\n" ); document.write( "Algebra- solving sytems of equations in three varaiables: \r
\n" ); document.write( "\n" ); document.write( "( Answer is needed within 1.5 hours, by 11\"30 AM Pacific time - Thanks!)\r
\n" ); document.write( "\n" ); document.write( "3x+5y+4z =13
\n" ); document.write( "5z+2y+3z=-9
\n" ); document.write( "6x+3y+4z=-8
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Algebra.Com's Answer #247883 by CharlesG2(834)\"\" \"About 
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Algebra- solving sytems of equations in three varaiables:
\n" ); document.write( "( Answer is needed within 1.5 hours, by 11\"30 AM Pacific time - Thanks!)
\n" ); document.write( "3x+5y+4z =13
\n" ); document.write( "5z+2y+3z=-9 (--> assuming this is 5x + 2y + 3z = -9)
\n" ); document.write( "6x+3y+4z=-8\r
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\n" ); document.write( "\n" ); document.write( "using method of elimination, choosing z first since I see two 4z's\r
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\n" ); document.write( "\n" ); document.write( "use 1st equation and multiply 3rd equation by -1\r
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\n" ); document.write( "\n" ); document.write( " 3x + 5y + 4z = 13
\n" ); document.write( "-6x - 3y - 4z = 8
\n" ); document.write( "add these to get -3x + 2y = 21\r
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\n" ); document.write( "\n" ); document.write( "use 1st equation multiplied by 3 and 2nd equation multipled by -4\r
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\n" ); document.write( "\n" ); document.write( " 9x + 15y + 12z = 39
\n" ); document.write( "-20x - 8y - 12z = 36
\n" ); document.write( "add these to get -11x + 7y = 75\r
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\n" ); document.write( "\n" ); document.write( "we now have:
\n" ); document.write( " -3x + 2y = 21 (multiply this one by 7)
\n" ); document.write( "-11x + 7y = 75 (multiply this one by -2)\r
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\n" ); document.write( "\n" ); document.write( "to get:
\n" ); document.write( "-21x + 14y = 147
\n" ); document.write( " 22x - 14y = -150
\n" ); document.write( "add these to get x = -3\r
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\n" ); document.write( "\n" ); document.write( "plug x = -3 into -3x + 2y = 21
\n" ); document.write( "-3(-3) + 2y = 21
\n" ); document.write( "9 + 2y = 21
\n" ); document.write( "2y = 12
\n" ); document.write( "y = 6\r
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\n" ); document.write( "\n" ); document.write( "now going back to the original equations, plug x = -3 and y = 6
\n" ); document.write( "into 3x + 5y + 4z = 13
\n" ); document.write( "3(-3) + 5(6) + 4z = 13
\n" ); document.write( "-9 + 30 + 4z = 13
\n" ); document.write( "21 + 4z = 13
\n" ); document.write( "4z = -8
\n" ); document.write( "z = -2\r
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\n" ); document.write( "\n" ); document.write( "solution is (-3,6,-2)\r
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\n" ); document.write( "\n" ); document.write( "hope this helps you\r
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