If f(x)= 1/1-x

Find the composition of f(f(x)).

So I get 1/1-(1/1-x)
I'm not sure if I am putting it in my calculator correctly because I keep getting a line. Is that right? If I put it in with the parentheses differently, I get the graph of f(x)=1/x.

Does anyone know which graph is right? Thanks in advance.

shouldnt u put it in as (1/1)-x

im not sure but try dat