How do you evaluate $log_3 81$ ?

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Answer 1 · 2015-02-05T12:12:43

The answer is $4$ because $3^4=81$

The question that the $log_a x$ function is posing is:

To what power do I have take $a$ to get to $x$

So in your case the question is:

To what power do I take $3$ to reach $81$ ?

Usually, you will be working with '10-logs' or 'e-logs'.
Those you can find on your calculator:

$log_10=log$ -button and $log_e=ln$ -button

If you use these buttons with shift or 2nd you get the opposite functions, the antilogs, marked as $10^x$ and $e^x$

How do you evaluate log_3 81log_3 81?