document.write( "Question 286328: express logarithm of log base c 5= a and log base c 4 =b \r
\n" ); document.write( "\n" ); document.write( "find log base c of 2\r
\n" ); document.write( "\n" ); document.write( "and log base c of 10
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Algebra.Com's Answer #207893 by jsmallt9(3758)\"\" \"About 
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\"log%28c%2C+%285%29%29+=+a\"
\n" ); document.write( "\"log%28c%2C+%284%29%29+=+b\"
\n" ); document.write( "To find \"log%28c%2C+%282%29%29\" we will need to use the properties on the base c logarithms we have. There are properties for products, quotients and powers of arguments. Since 4 is a power of 2 we can use \"log%28c%2C+%284%29%29+=+b\" and the property about powers in the argument of a logarithm to find \"log%28c%2C+%282%29%29\":
\n" ); document.write( "\"log%28c%2C+%284%29%29+=+b\"
\n" ); document.write( "\"log%28c%2C+%282%5E2%29%29+=+b\"
\n" ); document.write( "Using the property, \"log%28x%2C+%28p%5Eq%29%29+=+q%2Alog%28x%2C+%28q%29%29\", to move the exponent out of the argument:
\n" ); document.write( "\"2log%28c%2C+%282%29%29+=+b\"
\n" ); document.write( "Now we jsut divide by two:
\n" ); document.write( "\"log%28c%2C+%282%29%29+=+b%2F2\"

\n" ); document.write( "We now have three base c logarithms. For \"log%28c%2C+%2810%29%29\" we look for a product, quotient or power of 2, 4 and/or 5 which makes 10. Obviously 2*5=10 so:
\n" ); document.write( "\"log%28c%2C+%2810%29%29\"
\n" ); document.write( "\"log%28c%2C+%282%2A5%29%29\"
\n" ); document.write( "Now we can use the property for products in an argument, \"log%28x%2C+%28p%2Aq%29%29+=+log%28x%2C+%28p%29%29+%2B+log%28x%2C+%28q%29%29\", to separate the 2 and the 5:
\n" ); document.write( "\"log%28c%2C+%282%29%29+%2B+log%28c%2C+%285%29%29\"
\n" ); document.write( "We can replace these logarithms with what we know them to be:
\n" ); document.write( "\"b%2F2+%2B+a\"
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