Chapter 6 - Section 6.2 - One-to-One Functions; Inverse Functions - 6.2 Assess Your Understanding - Page 421: 68

$f^{-1}(x)=\frac{1}{x+3}$

$f(x)=\frac{-3x+1}{x},$ $y=\frac{-3x+1}{x},$ a.$x=\frac{-3y+1}{y},$ $xy=-3y+1,$ $xy+3y=1,$ $y(x+3)=1,$ $y=\frac{1}{x+3}=f^{-1}(x),$ b.Domain of $f(x)$ is $x\in \mathbb{R} \ne 0$ and Domain of $f^{-1}(x)$ is $x\in \mathbb{R} \ne -3$