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$$- \frac{\left(1 - \frac{x + 1}{x - 1}\right) \left(2 + \frac{1 - \frac{x + 1}{x - 1}}{\left(1 + \frac{\left(x + 1\right)^{2}}{\left(x - 1\right)^{2}}\right) \operatorname{atan}{\left(\frac{x + 1}{x - 1} \right)}} + \frac{2 \left(1 - \frac{x + 1}{x - 1}\right) \left(x + 1\right)}{\left(1 + \frac{\left(x + 1\right)^{2}}{\left(x - 1\right)^{2}}\right) \left(x - 1\right)}\right)}{\left(1 + \frac{\left(x + 1\right)^{2}}{\left(x - 1\right)^{2}}\right) \left(x - 1\right)^{2} \operatorname{atan}{\left(\frac{x + 1}{x - 1} \right)}} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = 41021.8488091042$$
$$x_{2} = -17469.436904434$$
$$x_{3} = 27461.2319329909$$
$$x_{4} = -39504.6751290796$$
$$x_{5} = -14927.3524472151$$
$$x_{6} = 36784.0709321344$$
$$x_{7} = -22554.0793735282$$
$$x_{8} = -38657.1150131125$$
$$x_{9} = 22376.3411939089$$
$$x_{10} = 14750.0085126649$$
$$x_{11} = 28308.7401281342$$
$$x_{12} = 13055.6231071968$$
$$x_{13} = 34241.4338131547$$
$$x_{14} = -31029.1794807115$$
$$x_{15} = 13902.789259839$$
$$x_{16} = -32724.2565413052$$
$$x_{17} = 21528.8944388227$$
$$x_{18} = -25944.0479680227$$
$$x_{19} = 37631.6220272009$$
$$x_{20} = 39326.7312335255$$
$$x_{21} = 35088.9766253215$$
$$x_{22} = -20859.1474952103$$
$$x_{23} = -35266.8952473857$$
$$x_{24} = -30181.6463301677$$
$$x_{25} = -42047.3659341353$$
$$x_{26} = 23223.7998488575$$
$$x_{27} = 15597.2717749299$$
$$x_{28} = -21706.6082476826$$
$$x_{29} = -19164.2623639488$$
$$x_{30} = -36962.0007124598$$
$$x_{31} = -23401.5597879998$$
$$x_{32} = -33571.7999220719$$
$$x_{33} = -26791.5572796802$$
$$x_{34} = 24071.2691047598$$
$$x_{35} = -20011.6983763845$$
$$x_{36} = 32546.3580302056$$
$$x_{37} = 18986.6421859638$$
$$x_{38} = -14080.0458297311$$
$$x_{39} = 20681.4611035732$$
$$x_{40} = 33393.8941961561$$
$$x_{41} = 29156.2540646245$$
$$x_{42} = 30003.7732427752$$
$$x_{43} = 35936.5224014566$$
$$x_{44} = 26613.7300444471$$
$$x_{45} = -15774.6892787207$$
$$x_{46} = 16444.5719168092$$
$$x_{47} = 18139.2612636203$$
$$x_{48} = 42716.9737385202$$
$$x_{49} = -41199.8006949158$$
$$x_{50} = 40174.2890427193$$
$$x_{51} = -16622.0519537387$$
$$x_{52} = 30851.2972192297$$
$$x_{53} = -40352.2370595654$$
$$x_{54} = 41869.4104114985$$
$$x_{55} = 31698.8255992445$$
$$x_{56} = -18316.841189787$$
$$x_{57} = -36114.4467995644$$
$$x_{58} = -27639.0722333254$$
$$x_{59} = -13232.7748377966$$
$$x_{60} = 24918.7478450127$$
$$x_{61} = -24249.048552373$$
$$x_{62} = -25096.5448501956$$
$$x_{63} = 25766.2351044339$$
$$x_{64} = -34419.3462259657$$
$$x_{65} = 19834.0429782806$$
$$x_{66} = -37809.556830925$$
$$x_{67} = 17291.9032681937$$
$$x_{68} = -31876.716310533$$
$$x_{69} = -28486.5923407423$$
$$x_{70} = -29334.1171684335$$
$$x_{71} = 38479.1755136064$$
Además hay que calcular los límites de y'' para los argumentos tendientes a los puntos de indeterminación de la función:
Puntos donde hay indeterminación:
$$x_{1} = 1$$
$$\lim_{x \to 1^-}\left(- \frac{\left(1 - \frac{x + 1}{x - 1}\right) \left(2 + \frac{1 - \frac{x + 1}{x - 1}}{\left(1 + \frac{\left(x + 1\right)^{2}}{\left(x - 1\right)^{2}}\right) \operatorname{atan}{\left(\frac{x + 1}{x - 1} \right)}} + \frac{2 \left(1 - \frac{x + 1}{x - 1}\right) \left(x + 1\right)}{\left(1 + \frac{\left(x + 1\right)^{2}}{\left(x - 1\right)^{2}}\right) \left(x - 1\right)}\right)}{\left(1 + \frac{\left(x + 1\right)^{2}}{\left(x - 1\right)^{2}}\right) \left(x - 1\right)^{2} \operatorname{atan}{\left(\frac{x + 1}{x - 1} \right)}}\right) = - \frac{1 \left(1 + 1 \pi\right)}{\pi^{2}}$$
$$\lim_{x \to 1^+}\left(- \frac{\left(1 - \frac{x + 1}{x - 1}\right) \left(2 + \frac{1 - \frac{x + 1}{x - 1}}{\left(1 + \frac{\left(x + 1\right)^{2}}{\left(x - 1\right)^{2}}\right) \operatorname{atan}{\left(\frac{x + 1}{x - 1} \right)}} + \frac{2 \left(1 - \frac{x + 1}{x - 1}\right) \left(x + 1\right)}{\left(1 + \frac{\left(x + 1\right)^{2}}{\left(x - 1\right)^{2}}\right) \left(x - 1\right)}\right)}{\left(1 + \frac{\left(x + 1\right)^{2}}{\left(x - 1\right)^{2}}\right) \left(x - 1\right)^{2} \operatorname{atan}{\left(\frac{x + 1}{x - 1} \right)}}\right) = \frac{1 \left(-1 + 1 \pi\right)}{\pi^{2}}$$
- los límites no son iguales, signo
$$x_{1} = 1$$
- es el punto de flexión
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:
No tiene corvaduras en todo el eje numérico