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$$\frac{6 \left(1 - \frac{2 \left(x + 1\right)}{x}\right) \sin{\left(\frac{x + 1}{x^{3}} \right)} - \frac{\left(1 - \frac{3 \left(x + 1\right)}{x}\right)^{2} \cos{\left(\frac{x + 1}{x^{3}} \right)}}{x^{2}}}{x^{4}} = 0$$
Solve this equationThe roots of this equation
$$x_{1} = 2445.02186617486$$
$$x_{2} = 1831.77557887171$$
$$x_{3} = 2547.23189930193$$
$$x_{4} = 1320.77157878238$$
$$x_{5} = -2410.56071100205$$
$$x_{6} = 350.410531890048$$
$$x_{7} = -2308.35194534626$$
$$x_{8} = -1030.87129272842$$
$$x_{9} = -1848.42282386093$$
$$x_{10} = -826.541609839608$$
$$x_{11} = -1081.96004718537$$
$$x_{12} = -316.404127778277$$
$$x_{13} = 248.535702364571$$
$$x_{14} = -928.700502250253$$
$$x_{15} = 2496.12682157665$$
$$x_{16} = 1014.20464288964$$
$$x_{17} = 1218.57821055566$$
$$x_{18} = -1950.62748256464$$
$$x_{19} = 1576.26754529992$$
$$x_{20} = 1422.96811411908$$
$$x_{21} = -724.40001086787$$
$$x_{22} = 147.034528836638$$
$$x_{23} = -2103.93660587723$$
$$x_{24} = -1541.81825069743$$
$$x_{25} = -1746.21954374864$$
$$x_{26} = -1695.11850083007$$
$$x_{27} = -2155.04013355135$$
$$x_{28} = -520.213676945911$$
$$x_{29} = -1388.52347028782$$
$$x_{30} = 299.447572811515$$
$$x_{31} = -775.468192937315$$
$$x_{32} = 605.568158278379$$
$$x_{33} = 2036.18770765754$$
$$x_{34} = -2512.7700861252$$
$$x_{35} = -265.636709054726$$
$$x_{36} = 1116.38884559409$$
$$x_{37} = 1729.57125095062$$
$$x_{38} = 1371.86949339593$$
$$x_{39} = 758.779650295457$$
$$x_{40} = -215.082687583676$$
$$x_{41} = 963.114968145746$$
$$x_{42} = -2052.83330908993$$
$$x_{43} = 912.027256789307$$
$$x_{44} = 1933.98112421753$$
$$x_{45} = 809.85913344181$$
$$x_{46} = -1235.23627772999$$
$$x_{47} = 2393.91704078416$$
$$x_{48} = -1899.52499515241$$
$$x_{49} = 1269.67445261585$$
$$x_{50} = 1627.3683636192$$
$$x_{51} = 554.510483970308$$
$$x_{52} = 197.707971711075$$
$$x_{53} = 2240.60343186634$$
$$x_{54} = 860.941841230184$$
$$x_{55} = 1882.87821146589$$
$$x_{56} = -1797.32099638419$$
$$x_{57} = -165.038538049771$$
$$x_{58} = -2257.24781749263$$
$$x_{59} = 2087.29134202277$$
$$x_{60} = -1286.33099158276$$
$$x_{61} = 1780.67324995643$$
$$x_{62} = -571.242230548255$$
$$x_{63} = -418.222608156793$$
$$x_{64} = 1167.48296439153$$
$$x_{65} = 503.46221614866$$
$$x_{66} = -2206.14387571627$$
$$x_{67} = -1644.01790696967$$
$$x_{68} = -622.284946439451$$
$$x_{69} = -367.281360542926$$
$$x_{70} = 1985.08429597335$$
$$x_{71} = -1592.91780671251$$
$$x_{72} = 656.633179621991$$
$$x_{73} = 1474.06736969493$$
$$x_{74} = -1184.14276379848$$
$$x_{75} = -1439.62101112991$$
$$x_{76} = -1490.71929673611$$
$$x_{77} = -1133.05061928288$$
$$x_{78} = -2359.45624693954$$
$$x_{79} = 1678.46961119571$$
$$x_{80} = -1337.42676272926$$
$$x_{81} = 1525.16719814361$$
$$x_{82} = 401.40688062945$$
$$x_{83} = 452.426264707941$$
$$x_{84} = 2291.70781414856$$
$$x_{85} = -979.784654936129$$
$$x_{86} = -469.204456022794$$
$$x_{87} = -877.619293922369$$
$$x_{88} = 2138.39518343623$$
$$x_{89} = -2001.73026130036$$
$$x_{90} = -2563.87497903253$$
$$x_{91} = 707.704049240195$$
$$x_{92} = 2189.49921769502$$
$$x_{93} = 1065.29600984657$$
$$x_{94} = -1.88774928825478$$
$$x_{95} = 2342.81235375021$$
$$x_{96} = -2461.66532721757$$
$$x_{97} = -673.338347966432$$
You also need to calculate the limits of y '' for arguments seeking to indeterminate points of a function:
Points where there is an indetermination:
$$x_{1} = 0$$
True
True
- 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
$$\left[-1.88774928825478, \infty\right)$$
Convex at the intervals
$$\left(-\infty, -1.88774928825478\right]$$