Prove that f is injective and serjective.
The Attempt at a Solution
I already proved that it's injective by stating the injectivity law:
for every (a,b)ε]1,+∞[: f(a)=f(b) implies a=b
so: 2a/(a-1)=2b/(b-1) entails: 2ab-2b=2ab-2a entails -2b=-2a entails a=b
Can anyone please tell me how to prove that its serjective?