How do you evaluate log_81 9?

1 Answer
George C.
Aug 16, 2016

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

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