document.write( "Question 171046: how do you condense a problem like \"+log3-log4-log7+\"? \n" ); document.write( "
Algebra.Com's Answer #126268 by solver91311(24713)\"\" \"About 
You can put this solution on YOUR website!

\n" ); document.write( "The appropriate logarithm rules to apply are:\r
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\n" ); document.write( "\n" ); document.write( "1. \"log%28b%2Cx%5B1%5D%29%2Blog%28b%2Cx%5B2%5D%29=log%28b%2C%28x%5B1%5D%2Ax%5B2%5D%29%29\" and\r
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\n" ); document.write( "\n" ); document.write( "2. \"log%28b%2Cx%5B1%5D%29-log%28b%2Cx%5B2%5D%29=log%28b%2C%28x%5B1%5D%2Fx%5B2%5D%29%29\"\r
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\n" ); document.write( "\n" ); document.write( "First thing is to apply the Associative and Distributive Properties:\r
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\n" ); document.write( "\n" ); document.write( "\"log%283%29-log%284%29-log%287%29=log%283%29-%28log%284%29%2Blog%287%29%29\"\r
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\n" ); document.write( "\n" ); document.write( "Now, using Rule 1., you can render the part in parentheses as:\r
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\n" ); document.write( "\n" ); document.write( "\"log%2828%29\" and substitute, thus:\r
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\n" ); document.write( "\n" ); document.write( "\"log%283%29-log%2828%29\"\r
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\n" ); document.write( "\n" ); document.write( "Now apply rule 2., thus:\r
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\n" ); document.write( "\n" ); document.write( "\"log%283%2F28%29\"\r
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\n" ); document.write( "\n" ); document.write( "Since \"3%2F28\" is already reduced to lowest terms, you are done.\r
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\n" ); document.write( "\n" ); document.write( "Check the reasonability of your answer with a calculator:\r
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\n" ); document.write( "\n" ); document.write( "\"log%283%29+=+0.4771\" (roughly)\r
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\n" ); document.write( "\n" ); document.write( "\"log%284%29+=+0.6021\" (roughly)\r
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\n" ); document.write( "\n" ); document.write( "\"log%287%29+=+0.8451\" (roughly)\r
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\n" ); document.write( "\n" ); document.write( "\"0.4771+-+0.6021+=+-0.125\" and \"-0.125+-+0.8451+=+-0.9701\"\r
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\n" ); document.write( "\n" ); document.write( "So far, so good. Since \"log%2810%2C1%29=0\", the log of something smaller than 1, in particular \"3%2F28\" must be less than zero.\r
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\n" ); document.write( "\n" ); document.write( "Again, from the calculator: \"3%2F28+=+0.1071\" (roughly) and \"log%280.1071%29+=+-0.9072\".\r
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\n" ); document.write( "\n" ); document.write( "Close enough. \r
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