If $$f(x)=\frac{|x|}{x}$$, for $$x \neq 0$$ $$=1$$, for $$x=0$$, then tre function is

The function $$f(x)=\frac{x+1}{9 x+x^3}$$ is

The points of discontinuity of the function

$$\begin{aligned} f(x) & =\frac{1}{x-1}, \text { if } 0 \leq x \leq 2 \\ & =\frac{x+5}{x+3} \text { if } 2< x \leq 4 \end{aligned}$$

in its domain are