document.write( "Question 1123266: 5x-9y=7
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Algebra.Com's Answer #739569 by ikleyn(52803) $\"\"$ $\"About$

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document.write( "5x - 9y =  7      \r\n" );
document.write( "7y - 3x = -5      \r\n" );
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document.write( "First, write it in the standard form\r\n" );
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document.write( " 5x - 9y =  7        (1)\r\n" );
document.write( "-3x + 7y = -5.       (2)\r\n" );
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document.write( "Apply the Elimination method.\r\n" );
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document.write( "For it, multiply equation  (2)  by 3  (both sides); then multiply equation (2) by 5 (both sides). \r\n" );
document.write( "You will get an equivalent system\r\n" );
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document.write( " 15x - 27y =  21     (3)\r\n" );
document.write( "-15x + 35y = -25.    (4)\r\n" );
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document.write( "Now add equations (3) and (4).  The x-terms will cancel each other, and  you will get a single equation for unknown y only:\r\n" );
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document.write( " -27y + 35y = 21 + (-25)\r\n" );
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document.write( "   8y = -4  \r\n" );
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document.write( "    y =  = -0.5.\r\n" );
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document.write( "Now from equation (1),  5x = 7 + 9y = 7 + 9*(-0.5) = 7 - 4.5 = 2.5  ====>  x =  = 0.5.\r\n" );
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document.write( "Answer.  x= 0.5;  y= -0.5.\r\n" );
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document.write( "Check.   Check the solution on your own by substituting into equations (1) and (2).\r\n" );
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\n" ); document.write( "\n" ); document.write( "On the way, you learned how the Elimination method works.\r
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