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$$\frac{6 \cdot \left(1 - \frac{2}{x^{2}}\right)}{x^{3}} = 0$$
Solve this equationThe roots of this equation
$$x_{1} = - \sqrt{2}$$
$$x_{2} = \sqrt{2}$$
You also need to calculate the limits of y '' for arguments seeking to indeterminate points of a function:
Points where there is an indetermination:
$$x_{1} = 0$$
$$\lim_{x \to 0^-}\left(\frac{6 \cdot \left(1 - \frac{2}{x^{2}}\right)}{x^{3}}\right) = \infty$$
Let's take the limit$$\lim_{x \to 0^+}\left(\frac{6 \cdot \left(1 - \frac{2}{x^{2}}\right)}{x^{3}}\right) = -\infty$$
Let's take the limit- the limits are not equal, so
$$x_{1} = 0$$
- is an inflection point
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
$$\left[\sqrt{2}, \infty\right)$$
Convex at the intervals
$$\left(-\infty, - \sqrt{2}\right]$$