Answer
(a) $ f^{-1}(x)=\frac{4}{x}$
(b) see graph
(c) $f(x)$ domain $(-\infty,0)U(0,\infty)$ and range $(-\infty,0)U(0,\infty)$, $f^{-1}(x)$ domain $(-\infty,0)U(0,\infty)$ and range $(-\infty,0)U(0,\infty)$.
Work Step by Step
(a) This function $f(x)=\frac{4}{x}, x\ne0$ is one-to-one. Find the inverse as the following: $y=\frac{4}{x}\longrightarrow x=\frac{4}{y}\longrightarrow f^{-1}(x)=\frac{4}{x}$
(b) see graph
(c) $f(x)$ domain $(-\infty,0)U(0,\infty)$ and range $(-\infty,0)U(0,\infty)$, $f^{-1}(x)$ domain $(-\infty,0)U(0,\infty)$ and range $(-\infty,0)U(0,\infty)$.