How do you evaluate #log_3 81#?

1 Answer
Feb 5, 2015

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#