document.write( "Question 83812: log (-x) + log (3) = log (2x-15) \r
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\n" ); document.write( "\n" ); document.write( "I got an answer of 5 but I am not sure if that is correct. \n" ); document.write( "
Algebra.Com's Answer #60290 by Edwin McCravy(20060)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "There is no solution.\r\n" );
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document.write( "log (-x) + log (3) = log (2x-15) \r\n" );
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document.write( "log[(-x)(3)] = log(2x-15)\r\n" );
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document.write( "log(-3x) = log(2x-15)\r\n" );
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document.write( "Since the logs are equal, what they are the logs\r\n" );
document.write( "of are also equal:\r\n" );
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document.write( "    -3x = 2x - 15\r\n" );
document.write( "    -5x = -15\r\n" );
document.write( "      x = 3 \r\n" );
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document.write( "However when we try to check:\r\n" );
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document.write( "log (-x) + log (3) = log (2x-15)\r\n" );
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document.write( "log(-3) + log(3) = log(2·3 - 15)\r\n" );
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document.write( "log(-3) is undefined. Logs cannot be \r\n" );
document.write( "taken of 0 or negative numbers, only of \r\n" );
document.write( "positive numbers, so the solution 3 is \r\n" );
document.write( "extraneous.\r\n" );
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document.write( "log(-3) + log(3) = log(6-15)\r\n" );
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document.write( "log(-3) + log(3) = log(-9)\r\n" );
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document.write( "There is no solution.\r\n" );
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document.write( "Of course your answer of 5\r\n" );
document.write( "does not check either, but you\r\n" );
document.write( "must have solved it wrong to have\r\n" );
document.write( "gotten 5 instead of 3.\r\n" );
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document.write( "Edwin
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