document.write( "Question 4281: How do you work out the percentage increase/decrease between two figures?
\n" ); document.write( "Example. What is the percent increase/decrease from 41210 to 38853? \n" ); document.write( "
Algebra.Com's Answer #1916 by AnlytcPhil(1806)\"\" \"About 
You can put this solution on YOUR website!
Prove that:
\n" ); document.write( "(logax·logbx)/(logax + logbx) =logabx
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\n" ); document.write( "We must assume that a, b, and x are all positive
\n" ); document.write( "and different from 1, otherwise the above is not defined.
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\n" ); document.write( "We need two rules of logarithms
\n" ); document.write( "(1) logmn = 1/lognm, when m and n are positive but neither is 1
\n" ); document.write( "(2) logmp + logmq = logm(pq), when m,p,q are positive and m is not 1
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\n" ); document.write( "Use (1) to replace every term in left hand side\r
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document.write( "      1         1\r\n" );
document.write( "   ------- · -------\r\n" );
document.write( "    logxa     logxb\r\n" );
document.write( "-----------------------\r\n" );
document.write( "    1          1\r\n" );
document.write( " ------- + --------\r\n" );
document.write( "  logxa      logxb\r\n" );
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document.write( "Multiply top and bottom by logxa·logxb\r\n" );
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document.write( "\r\n" );
document.write( "        1\r\n" );
document.write( "--------------------\r\n" );
document.write( " logxb + logxa\r\n" );
document.write( " \r\n" );
document.write( "      1\r\n" );
document.write( "------------\r\n" );
document.write( "  logx(ba)\r\n" );
document.write( " \r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "` use (1)\r\n" );
document.write( "\r\n" );
document.write( "       1\r\n" );
document.write( " ------------\r\n" );
document.write( "       1\r\n" );
document.write( "   --------\r\n" );
document.write( "    logbax\r\n" );
document.write( " \r\n" );
document.write( "\r\n" );
document.write( "     logbax\r\n" );
document.write( "\r\n" );
document.write( "     logabx\r\n" );
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\r
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