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$$\frac{\frac{2 \log{\left(6 x \right)}}{\left(x + 6\right)^{2}} - \frac{2}{x \left(x + 6\right)} - \frac{1}{x^{2}}}{x + 6} = 0$$
Solve this equationThe roots of this equation
$$x_{1} = 42514.0197126849$$
$$x_{2} = 44595.665429855$$
$$x_{3} = 54989.4041088202$$
$$x_{4} = 50835.1171488098$$
$$x_{5} = 6.69656678575869$$
$$x_{6} = 46676.4702816404$$
$$x_{7} = 40431.7067631467$$
$$x_{8} = 27949.5664707624$$
$$x_{9} = 26914.6814181565$$
$$x_{10} = 38348.9767867252$$
$$x_{11} = 49795.8499616273$$
$$x_{12} = 30024.098021514$$
$$x_{13} = 47716.5183302058$$
$$x_{14} = 37307.5625704563$$
$$x_{15} = 25882.0101643839$$
$$x_{16} = 36266.1905436718$$
$$x_{17} = 53951.2568344188$$
$$x_{18} = 32102.7899925164$$
$$x_{19} = 35224.9316224061$$
$$x_{20} = 43554.9383137055$$
$$x_{21} = 51874.1102610085$$
$$x_{22} = 39390.3744480501$$
$$x_{23} = 33143.1152657172$$
$$x_{24} = 34183.871705079$$
$$x_{25} = 41472.9331284706$$
$$x_{26} = 52912.8246738068$$
$$x_{27} = 31063.0528403066$$
$$x_{28} = 48756.3145754334$$
$$x_{29} = 58102.1214499038$$
$$x_{30} = 57064.8372940295$$
$$x_{31} = 45636.1815004787$$
$$x_{32} = 56027.2646514781$$
$$x_{33} = 28986.1676948273$$
You also need to calculate the limits of y '' for arguments seeking to indeterminate points of a function:
Points where there is an indetermination:
$$x_{1} = -6$$
$$\lim_{x \to -6^-}\left(\frac{\frac{2 \log{\left(6 x \right)}}{\left(x + 6\right)^{2}} - \frac{2}{x \left(x + 6\right)} - \frac{1}{x^{2}}}{x + 6}\right) = - \infty \operatorname{sign}{\left(7.16703787691222 + 2 i \pi \right)}$$
$$\lim_{x \to -6^+}\left(\frac{\frac{2 \log{\left(6 x \right)}}{\left(x + 6\right)^{2}} - \frac{2}{x \left(x + 6\right)} - \frac{1}{x^{2}}}{x + 6}\right) = \infty \operatorname{sign}{\left(7.16703787691222 + 2 i \pi \right)}$$
- the limits are not equal, so
$$x_{1} = -6$$
- 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
$$\left[6.69656678575869, \infty\right)$$
Convex at the intervals
$$\left(-\infty, 6.69656678575869\right]$$