If [tex]f^{-1}(x)[/tex] is the inverse of [tex]f(x)[/tex], then by definition
[tex]f\left(f^{-1}(x)\right) = x[/tex]
so that
[tex]2 \times 3^{f^{-1}(x)} = x[/tex]
Solve for [tex]f^{-1}(x)[/tex] :
[tex]3^{f^{-1}(x)} = \dfrac x2[/tex]
[tex]\log_3\left(3^{f^{-1}(x)}\right) = \log_3\left(\dfrac x2\right)[/tex]
[tex]f^{-1}(x) \log_3(3) = \log_3\left(\dfrac x2\right)[/tex]
[tex]\boxed{f^{-1}(x) = \log_3\left(\dfrac x2\right)}[/tex]
