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$$\frac{3 x \left(- \frac{3 x^{3}}{x^{3} - 1} + 2\right)}{x^{3} - 1} = 0$$
Solve this equationThe roots of this equation
$$x_{1} = 0$$
$$x_{2} = - \sqrt[3]{2}$$
Сonvexity and concavity intervals:Let’s find the intervals where the function is convex or concave, for this look at the behaviour of the function at the inflection points:
Concave at the intervals
$$\left[- \sqrt[3]{2}, 0\right]$$
Convex at the intervals
$$\left(-\infty, - \sqrt[3]{2}\right] \cup \left[0, \infty\right)$$