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).