document.write( "Question 278554: Evaluate the logarithmic expression 1-log[5]21 \n" ); document.write( "

Algebra.Com's Answer #202953 by jsmallt9(3758) $\"\"$ $\"About$

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If the problem is:
\n" ); document.write( " $\"1+-+log%285%2C+%2821%29%29\"$
\n" ); document.write( "then, since no calculator I know \"knows\" base 5 logrithms, we need to convert this logarithm to a base our calculator does \"know\", like base 10 or base e (ln). There is a base conversion formula for this:
\n" ); document.write( " $\"log%28a%2C+%28p%29%29+=+log%28b%2C+%28p%29%29%2Flog%28b%2C+%28a%29%29\"$
\n" ); document.write( "Using this to convert the base 5 logarithm into a base 10 logarithm we get:
\n" ); document.write( " $\"1+-+log%28%2821%29%29%2Flog%28%285%29%29\"$
\n" ); document.write( "Now you can use your calculators to find the two logarithms, divide them and then subtract that from 1. (Be sure to use this order. Do not divide 21 by 5 first and then find the logarithm. That will not give you the correct answer.) \n" ); document.write( "

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