Hallemos los puntos de flexiones, para eso hay que resolver la ecuación
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = 0$$
(la segunda derivada es igual a cero),
las raíces de la ecuación obtenida serán los puntos de flexión para el gráfico de la función indicado:
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = $$
segunda derivada$$\frac{2 \left(\left(\tan^{2}{\left(x \right)} + 1\right) \tan{\left(x \right)} - \frac{\left(\tan^{2}{\left(x \right)} + 1\right) \left(4 x^{3} + 2 x + 1\right)}{x \left(x^{3} + x + 1\right)} - \frac{\left(6 x^{2} + 1 - \frac{\left(4 x^{3} + 2 x + 1\right)^{2}}{x \left(x^{3} + x + 1\right)}\right) \tan{\left(x \right)}}{x \left(x^{3} + x + 1\right)}\right)}{x \left(x^{3} + x + 1\right)} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = -37.8037755037868$$
$$x_{2} = 56.6189696063376$$
$$x_{3} = -94.2901266175658$$
$$x_{4} = 59.7569038287361$$
$$x_{5} = -47.2080280671997$$
$$x_{6} = 25.2871809599612$$
$$x_{7} = 31.540786181549$$
$$x_{8} = -59.7569042920565$$
$$x_{9} = 97.430358940554$$
$$x_{10} = -81.7302350898235$$
$$x_{11} = 44.0723281206025$$
$$x_{12} = 3.76166887818915$$
$$x_{13} = -34.6714087410708$$
$$x_{14} = -66.0338025277351$$
$$x_{15} = -88.0099512251226$$
$$x_{16} = 12.8522465937936$$
$$x_{17} = 69.1726744432842$$
$$x_{18} = -22.1661425637521$$
$$x_{19} = -62.8951985607164$$
$$x_{20} = -53.4814581946947$$
$$x_{21} = -28.4124622404836$$
$$x_{22} = -3.76569172914575$$
$$x_{23} = -9.78197986317429$$
$$x_{24} = -31.54079192294$$
$$x_{25} = 81.7302349564664$$
$$x_{26} = 94.2901265421304$$
$$x_{27} = -84.8700294395875$$
$$x_{28} = -44.0723296666291$$
$$x_{29} = -12.8524108556204$$
$$x_{30} = 47.2080268885788$$
$$x_{31} = 75.4510914276076$$
$$x_{32} = 19.0510501465303$$
$$x_{33} = -50.3444452694666$$
$$x_{34} = 66.0338022161497$$
$$x_{35} = 62.8951981826111$$
$$x_{36} = 91.1499873087187$$
$$x_{37} = -40.9375091321834$$
$$x_{38} = -78.5905832846552$$
$$x_{39} = 37.8037726761926$$
$$x_{40} = 15.9448296005744$$
$$x_{41} = 88.0099511258307$$
$$x_{42} = 72.3117804442317$$
$$x_{43} = -15.9449057266939$$
$$x_{44} = 40.9375070645391$$
$$x_{45} = 9.78156791301043$$
$$x_{46} = 78.5905831287815$$
$$x_{47} = 22.1661202398505$$
$$x_{48} = 53.4814574752989$$
$$x_{49} = -19.0510896342101$$
$$x_{50} = -25.2871944587931$$
$$x_{51} = 100.570675841292$$
$$x_{52} = 50.3444443555414$$
$$x_{53} = 34.6714047727383$$
$$x_{54} = -6.74793974598142$$
$$x_{55} = -100.570675899621$$
$$x_{56} = 84.8700293248275$$
$$x_{57} = 6.74668135662241$$
$$x_{58} = -56.6189701802256$$
$$x_{59} = -75.4510916109501$$
$$x_{60} = -91.1499873950612$$
$$x_{61} = -72.31178066136$$
$$x_{62} = -97.4303590067504$$
$$x_{63} = 28.4124536274274$$
$$x_{64} = -69.1726747023379$$
Además hay que calcular los límites de y'' para los argumentos tendientes a los puntos de indeterminación de la función:
Puntos donde hay indeterminación:
$$x_{1} = -0.682327803828019$$
$$x_{2} = 0$$
$$\lim_{x \to -0.682327803828019^-}\left(\frac{2 \left(\left(\tan^{2}{\left(x \right)} + 1\right) \tan{\left(x \right)} - \frac{\left(\tan^{2}{\left(x \right)} + 1\right) \left(4 x^{3} + 2 x + 1\right)}{x \left(x^{3} + x + 1\right)} - \frac{\left(6 x^{2} + 1 - \frac{\left(4 x^{3} + 2 x + 1\right)^{2}}{x \left(x^{3} + x + 1\right)}\right) \tan{\left(x \right)}}{x \left(x^{3} + x + 1\right)}\right)}{x \left(x^{3} + x + 1\right)}\right) = -2.96208916467994 \cdot 10^{48}$$
$$\lim_{x \to -0.682327803828019^+}\left(\frac{2 \left(\left(\tan^{2}{\left(x \right)} + 1\right) \tan{\left(x \right)} - \frac{\left(\tan^{2}{\left(x \right)} + 1\right) \left(4 x^{3} + 2 x + 1\right)}{x \left(x^{3} + x + 1\right)} - \frac{\left(6 x^{2} + 1 - \frac{\left(4 x^{3} + 2 x + 1\right)^{2}}{x \left(x^{3} + x + 1\right)}\right) \tan{\left(x \right)}}{x \left(x^{3} + x + 1\right)}\right)}{x \left(x^{3} + x + 1\right)}\right) = -2.96208916467994 \cdot 10^{48}$$
- los límites son iguales, es decir omitimos el punto correspondiente
$$\lim_{x \to 0^-}\left(\frac{2 \left(\left(\tan^{2}{\left(x \right)} + 1\right) \tan{\left(x \right)} - \frac{\left(\tan^{2}{\left(x \right)} + 1\right) \left(4 x^{3} + 2 x + 1\right)}{x \left(x^{3} + x + 1\right)} - \frac{\left(6 x^{2} + 1 - \frac{\left(4 x^{3} + 2 x + 1\right)^{2}}{x \left(x^{3} + x + 1\right)}\right) \tan{\left(x \right)}}{x \left(x^{3} + x + 1\right)}\right)}{x \left(x^{3} + x + 1\right)}\right) = \frac{8}{3}$$
$$\lim_{x \to 0^+}\left(\frac{2 \left(\left(\tan^{2}{\left(x \right)} + 1\right) \tan{\left(x \right)} - \frac{\left(\tan^{2}{\left(x \right)} + 1\right) \left(4 x^{3} + 2 x + 1\right)}{x \left(x^{3} + x + 1\right)} - \frac{\left(6 x^{2} + 1 - \frac{\left(4 x^{3} + 2 x + 1\right)^{2}}{x \left(x^{3} + x + 1\right)}\right) \tan{\left(x \right)}}{x \left(x^{3} + x + 1\right)}\right)}{x \left(x^{3} + x + 1\right)}\right) = \frac{8}{3}$$
- los límites son iguales, es decir omitimos el punto correspondiente
Intervalos de convexidad y concavidad:Hallemos los intervales donde la función es convexa o cóncava, para eso veamos cómo se comporta la función en los puntos de flexiones:
Cóncava en los intervalos
$$\left[100.570675841292, \infty\right)$$
Convexa en los intervalos
$$\left(-\infty, -100.570675899621\right]$$