document.write( "Question 387373: why would logarithms give me extraneous solutions? \n" ); document.write( "
Algebra.Com's Answer #273819 by Edwin McCravy(20056)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "Because logarithms can only be taken of positive numbers, and\r\n" );
document.write( "a logarithm equation just might be converted to an equation that\r\n" );
document.write( "has a 0 or negative solution.\r\n" );
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document.write( " log(13 – 5x) = log(1 – x)\r\n" );
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document.write( "We use the principle that we convert log(A) = log(B) to A = B\r\n" );
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document.write( "    13 - 5x = 1 - x\r\n" );
document.write( "        -4x = -12\r\n" );
document.write( "          x = 3\r\n" );
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document.write( "But when you check it you find that this is an extraneous solution:\r\n" );
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document.write( " log(13 – 5(3)) = log(1 – 3)\r\n" );
document.write( "   log(13 - 15) = log(-2)\r\n" );
document.write( "        log(-2) = log(-2)\r\n" );
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document.write( "This may look like it checks except for the fact that logs of negative\r\n" );
document.write( "numbers do not exist in real numbers.  So there is no solution in\r\n" );
document.write( "real numbers.\r\n" );
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document.write( "Edwin
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