Question

How do you evaluate `log_81 9`?

Answer 1

Use the change of base formula to find:

`log_81 9 = 1/2`

Explanation:

The change of base formula tells us that for any `a, b, c > 0` with `b, c != 1`

`log_a b = (log_c b) / (log_c a)`

So we find:

`log_81 9 = log_9 9 / log_9 81 = log_9 9 / log_9 9^2 = 1/2`