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$$\frac{1}{\left(x - 4\right)^{2}} + \frac{x - 3}{2 \left(1 - \left(x - 3\right)^{2}\right)^{\frac{3}{2}}} = 0$$
Solve this equationThe roots of this equation
$$x_{1} = - \frac{59}{225 \sqrt[3]{\frac{289}{3375} + \frac{2 \sqrt{321}}{225}}} + \sqrt[3]{\frac{289}{3375} + \frac{2 \sqrt{321}}{225}} + \frac{34}{15}$$
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
$$\left[- \frac{59}{225 \sqrt[3]{\frac{289}{3375} + \frac{2 \sqrt{321}}{225}}} + \sqrt[3]{\frac{289}{3375} + \frac{2 \sqrt{321}}{225}} + \frac{34}{15}, \infty\right)$$
Convex at the intervals
$$\left(-\infty, - \frac{59}{225 \sqrt[3]{\frac{289}{3375} + \frac{2 \sqrt{321}}{225}}} + \sqrt[3]{\frac{289}{3375} + \frac{2 \sqrt{321}}{225}} + \frac{34}{15}\right]$$