For $$f(x)=[x]$$, where $$[x]$$ is the greatest integer function, which of the following is true, for every $$x \in \mathbf{R}$$

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

The approximate value of the function $$f(x)=x^3-3 x+5$$ at $$x=1.99$$ is

If $$f(x)=\frac{2 x+3}{3 x-2}, x \neq \frac{2}{3}$$, then the function $$f$$ of is