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$$\frac{2 \left(\left(x + 3\right) \left(\frac{4 x^{2}}{x^{2} - 9} - 1\right) - 2 x\right)}{\left(x^{2} - 9\right)^{2}} = 0$$
Solve this equationSolutions are not found,
maybe, the function has no inflections