Let's find the inflection points, we'll need to solve the equation for this
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = 0$$
(the second derivative equals zero),
the roots of this equation will be the inflection points for the specified function graph:
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = $$
the second derivative$$\frac{2 \left(- \frac{\left(1 - \frac{\left(2 x - 3\right)^{2}}{x \left(x - 3\right)}\right) \left(x - 9\right)}{x - 3} + 1 - \frac{\left(2 x - 9\right) \left(2 x - 3\right)}{x \left(x - 3\right)}\right)}{x \left(x - 3\right)} = 0$$
Solve this equationSolutions are not found,
maybe, the function has no inflections