Then 2 x > 2 (2x)

Then x > 2x

That is, x < 0.

Therefore, the domain of the function f(x) is {x/x < 0}.

And x- 1 < 0 and x+ 1≠0.

Know x < 1, x≦- 1.

So the domain of the function is (negative infinity,-1)∨(- 1, 1).