Find the inverse function of \( f \). \[ f(x)=6 x^{3}+8 \] \[ f^{-1}(x)= \] Find the inverse function of \( f \). \[ f(x)=\frac{3 x}{x-8} \] \[ f^{-1}(x)= \] Find the inverse function of \( f \). \[