Hallemos los puntos de flexiones, para eso hay que resolver la ecuación
$$\frac{d^{2}}{d y^{2}} f{\left(y \right)} = 0$$
(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:
$$\frac{d^{2}}{d y^{2}} f{\left(y \right)} = $$
segunda derivada$$\frac{\sqrt{2} \left(\operatorname{sign}{\left(y \right)} - \frac{\left|{y}\right|}{y}\right)}{y} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$y_{1} = 28$$
$$y_{2} = -22$$
$$y_{3} = -54$$
$$y_{4} = -32$$
$$y_{5} = -38$$
$$y_{6} = 32$$
$$y_{7} = 82$$
$$y_{8} = 76$$
$$y_{9} = -58$$
$$y_{10} = -86$$
$$y_{11} = -50$$
$$y_{12} = 86$$
$$y_{13} = 80$$
$$y_{14} = -64$$
$$y_{15} = -100$$
$$y_{16} = 36$$
$$y_{17} = -12$$
$$y_{18} = 38$$
$$y_{19} = -20$$
$$y_{20} = -8$$
$$y_{21} = -10$$
$$y_{22} = -44$$
$$y_{23} = 66$$
$$y_{24} = -62$$
$$y_{25} = -46$$
$$y_{26} = -48$$
$$y_{27} = 50$$
$$y_{28} = -74$$
$$y_{29} = 4$$
$$y_{30} = 98$$
$$y_{31} = -2$$
$$y_{32} = -66$$
$$y_{33} = 2$$
$$y_{34} = -28$$
$$y_{35} = 78$$
$$y_{36} = -92$$
$$y_{37} = 20$$
$$y_{38} = 54$$
$$y_{39} = 40$$
$$y_{40} = -40$$
$$y_{41} = 90$$
$$y_{42} = 74$$
$$y_{43} = 10$$
$$y_{44} = -76$$
$$y_{45} = 60$$
$$y_{46} = -18$$
$$y_{47} = -98$$
$$y_{48} = -36$$
$$y_{49} = 58$$
$$y_{50} = -30$$
$$y_{51} = 34$$
$$y_{52} = 18$$
$$y_{53} = -60$$
$$y_{54} = 70$$
$$y_{55} = 14$$
$$y_{56} = 30$$
$$y_{57} = 24$$
$$y_{58} = 64$$
$$y_{59} = -84$$
$$y_{60} = 26$$
$$y_{61} = 84$$
$$y_{62} = 52$$
$$y_{63} = 56$$
$$y_{64} = 68$$
$$y_{65} = 44$$
$$y_{66} = 94$$
$$y_{67} = 96$$
$$y_{68} = -26$$
$$y_{69} = 48$$
$$y_{70} = -14$$
$$y_{71} = -78$$
$$y_{72} = 6$$
$$y_{73} = -90$$
$$y_{74} = 16$$
$$y_{75} = -82$$
$$y_{76} = -34$$
$$y_{77} = 92$$
$$y_{78} = 42$$
$$y_{79} = -4$$
$$y_{80} = -56$$
$$y_{81} = 72$$
$$y_{82} = -72$$
$$y_{83} = -52$$
$$y_{84} = -16$$
$$y_{85} = -42$$
$$y_{86} = -6$$
$$y_{87} = 8$$
$$y_{88} = -24$$
$$y_{89} = -68$$
$$y_{90} = 88$$
$$y_{91} = -94$$
$$y_{92} = 46$$
$$y_{93} = -88$$
$$y_{94} = 22$$
$$y_{95} = -96$$
$$y_{96} = -70$$
$$y_{97} = -80$$
$$y_{98} = 100$$
$$y_{99} = 12$$
$$y_{100} = 62$$
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
$$\left[-30, 30\right]$$
Convexa en los intervalos
$$\left(-\infty, -30\right] \cup \left[30, \infty\right)$$