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$$\frac{2 \left(- \frac{2 x \left(4 x + 9\right)}{2 x^{2} + 9 x + 4} + \frac{\left(x^{2} - 16\right) \left(\frac{\left(4 x + 9\right)^{2}}{2 x^{2} + 9 x + 4} - 2\right)}{2 x^{2} + 9 x + 4} + 1\right)}{2 x^{2} + 9 x + 4} = 0$$
Solve this equationSolutions are not found,
maybe, the function has no inflections