I was looking for a fast way of getting which function is surjective and injective. So I tried to find such command in wolfram and surprisingly it says to me that $ln(x)$ is not injective. Link to proof: http://www.wolframalpha.com/input/?i=ln%28x%29+is+injective%3F
The questions are:
(1) Why did Wolfram|Alpha say that it is not injective?
(2) How the injectivity is defined in Wolfram?