If $$g(x) = {1 \over {f(x)}}$$ and f(x) = x, x $$\ne$$ 0, then which one of the following is correct?

The domain of the function $$f(x) = {1 \over {\sqrt {|x| - x} }}$$ is

If f : R $$\to$$ R, g : R $$\to$$ R are two functions given by f(x) = 2x $$-$$ 3 and g(x) = x³ + 5, then (fog)^$$-$$1 (x) is equal to

f(xy) = f(x) + f(y) is true for all