document.write( "Question 938281: How would I use the method of substitution to solve this problem?
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Algebra.Com's Answer #571705 by Edwin McCravy(20055)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "-x+2y = 2\r\n" );
document.write( " x-2y = -2\r\n" );
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document.write( "Solve the second one for x   x-2y = -2\r\n" );
document.write( "                                x = -2+2y\r\n" );
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document.write( "Substitute (-2+2y) for x in the first one:\r\n" );
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document.write( "      x-2y = -2\r\n" );
document.write( "(-2+2y)-2y = -2\r\n" );
document.write( "  -2+2y-2y = -2\r\n" );
document.write( "        -2 = -2\r\n" );
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document.write( "This equation -2 = -2 is an identity.\r\n" );
document.write( "When trying to solve using substitution or elimination, if we get an\r\n" );
document.write( "identity, that means there are infinitely many solutions. The graphs are the\r\n" );
document.write( "same line.\r\n" );
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document.write( "Answer: There are infinitely many solutions.  This is called\r\n" );
document.write( "a DEPENDENT SYSTEM.\r\n" );
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document.write( "[Note: BTW, in other problems when trying to solve using substitution \r\n" );
document.write( "or elimination, if we get a contradiction, such as -2 = -1, that means there\r\n" );
document.write( "are NO solutions. The graphs are parallel lines.  That would be called an\r\n" );
document.write( "INCONSISTENT SYSTEM.]\r\n" );
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document.write( "Edwin
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