# Is the logarithm function injective (one-to-one)?

Is the logarithm function injective (or, one-to-one)?

In other words, does $\log_2(x) = \log_2(y) \implies x = y$?

I.e., as $x$ and $y$ are in the same log base, can I just drop the logs?

Thanks!

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You asked a question of which this is clearly a special case in February. Is there something that wasn't cleared up by the answers there? –  Jonas Meyer May 22 '11 at 19:05

What does it mean for a number $a$ to be equal to $\log_2(x)$? It means that $2^a=x$.
Ah yes thank you, so $2^a = x = y$ hence $x = y$ correct? –  Danny King May 22 '11 at 14:31
More like $2^a = 2^b$ and thus $2^{a-b} = 1$. –  M.B. May 22 '11 at 14:33
More like $a=b$ and thus $2^a=2^b$. –  GEdgar May 22 '11 at 19:04