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$$\frac{8 x \left(\frac{4 x^{2}}{x^{2} + 4} - 3 + \frac{8 \left(\frac{2 x^{2}}{x^{2} + 4} - 1\right)^{2}}{\left(x^{2} + 4\right) \left(- \frac{16 x^{2}}{\left(x^{2} + 4\right)^{2}} + 1\right)}\right)}{\left(x^{2} + 4\right)^{2} \sqrt{- \frac{16 x^{2}}{\left(x^{2} + 4\right)^{2}} + 1}} = 0$$
Solve this equationThe roots of this equation
$$x_{1} = 0$$
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
$$\left(-\infty, 0\right]$$
Convex at the intervals
$$\left[0, \infty\right)$$