$\"\"$

The function is $\"\"$

f is increasing over its entire domain, $\"\"$ . To verify this, note that $\"\"$ is positive on the domain of f. So, f is strictly monotonic and it must have an inverse function. To find an equation for the inverse function, let y = f(x) and solve for x in terms of y.

$\"\"$ (Let y = f(x))

$\"\"$ (Divide each side by 3)

$\"\"$ (Interchange x and y)

$\"\"$ (Replace y by $\"\"$ )

$\"\"$

Graphically

$\"\"$

Therefore $\"\"$ and $\"\"$ .