Para hallar los extremos hay que resolver la ecuación
$$\frac{d}{d x} f{\left(x \right)} = 0$$
(la derivada es igual a cero),
y las raíces de esta ecuación serán los extremos de esta función:
$$\frac{d}{d x} f{\left(x \right)} = $$
primera derivada$$- \frac{18 x \operatorname{atan}^{2}{\left(3 x \right)}}{\left(9 x^{2} + 1\right)^{2}} + \frac{6 \operatorname{atan}{\left(3 x \right)}}{\left(9 x^{2} + 1\right)^{2}} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = -25453.3897677548$$
$$x_{2} = -16130.4206813256$$
$$x_{3} = 40841.0607305034$$
$$x_{4} = 14566.645056127$$
$$x_{5} = 9482.13453755639$$
$$x_{6} = -41557.4194475537$$
$$x_{7} = 33212.7888402883$$
$$x_{8} = 23889.4907884857$$
$$x_{9} = 37450.7092635504$$
$$x_{10} = -29691.2445869544$$
$$x_{11} = -15282.9195645598$$
$$x_{12} = -27996.0965725767$$
$$x_{13} = -39862.2411907947$$
$$x_{14} = 26432.1838705652$$
$$x_{15} = -12740.4998376586$$
$$x_{16} = 42536.2403963004$$
$$x_{17} = 22194.3774317304$$
$$x_{18} = 38298.2960378627$$
$$x_{19} = 15414.1359312968$$
$$x_{20} = 31517.6283055379$$
$$x_{21} = -33929.1412071627$$
$$x_{22} = 17956.6734820545$$
$$x_{23} = -30538.8211274058$$
$$x_{24} = -39014.653052031$$
$$x_{25} = -37319.478979684$$
$$x_{26} = 41688.6502691788$$
$$x_{27} = -19520.5156124822$$
$$x_{28} = 28974.898092493$$
$$x_{29} = -21215.6020344714$$
$$x_{30} = 34907.9540572246$$
$$x_{31} = 35755.5382122508$$
$$x_{32} = 30670.0500381674$$
$$x_{33} = 21346.8264711072$$
$$x_{34} = 7787.62982828489$$
$$x_{35} = -34776.7241948771$$
$$x_{36} = -32233.9786046248$$
$$x_{37} = -36471.8931491507$$
$$x_{38} = -22063.1523419379$$
$$x_{39} = 32365.2079413765$$
$$x_{40} = 25584.6168473202$$
$$x_{41} = -33081.5593147672$$
$$x_{42} = 34060.3709074307$$
$$x_{43} = -14435.4307255607$$
$$x_{44} = 12871.7087953663$$
$$x_{45} = -18672.9808002007$$
$$x_{46} = 29822.4732567211$$
$$x_{47} = -11893.0645713475$$
$$x_{48} = -13587.9564959512$$
$$x_{49} = 17109.1517713068$$
$$x_{50} = -17825.4526639404$$
$$x_{51} = -20368.0562591866$$
$$x_{52} = 11176.856602686$$
$$x_{53} = -22910.7066742105$$
$$x_{54} = -26300.9564102858$$
$$x_{55} = 10329.4752210354$$
$$x_{56} = 39993.4718178721$$
$$x_{57} = -28843.6696853761$$
$$x_{58} = 20499.2799588917$$
$$x_{59} = -38167.0656319192$$
$$x_{60} = -7656.46446138043$$
$$x_{61} = 18804.2027113685$$
$$x_{62} = -40709.8300031049$$
$$x_{63} = 0$$
$$x_{64} = 19651.7384765184$$
$$x_{65} = 39145.883572156$$
$$x_{66} = -24605.8257360461$$
$$x_{67} = 24737.0523946641$$
$$x_{68} = -9350.94656395263$$
$$x_{69} = -8503.66844061373$$
$$x_{70} = -10198.2799749787$$
$$x_{71} = 36603.1233022994$$
$$x_{72} = 16261.6387692744$$
$$x_{73} = 23041.9323456187$$
$$x_{74} = -35624.3081992955$$
$$x_{75} = -16977.9322153433$$
$$x_{76} = 28127.3246927144$$
$$x_{77} = -23758.2645969239$$
$$x_{78} = -42405.0094860591$$
$$x_{79} = -31386.3991731197$$
$$x_{80} = 27279.753223048$$
$$x_{81} = 13719.1683935771$$
$$x_{82} = -27148.5254173193$$
$$x_{83} = 8634.84682209105$$
$$x_{84} = 12024.2699308479$$
$$x_{85} = -11045.6557119668$$
Signos de extremos en los puntos:
(-25453.389767754827, 4.23154289069959e-10)
(-16130.420681325562, 1.05364528878586e-9)
(40841.060730503355, 1.64360973620241e-10)
(14566.64505612695, 1.29200892830183e-9)
(9482.13453755639, 3.04905725165556e-9)
(-41557.419447553664, 1.58743395577554e-10)
(33212.78884028826, 2.48531251177041e-10)
(23889.490788485706, 4.80369852242893e-10)
(37450.709263550416, 1.95466451487248e-10)
(-29691.24458695437, 3.10981269046097e-10)
(-15282.919564559794, 1.1737416859579e-9)
(-27996.09657257674, 3.497805810516e-10)
(-39862.241190794666, 1.72531816782174e-10)
(26432.183870565226, 3.92395644092528e-10)
(-12740.499837658586, 1.68892297509467e-9)
(42536.24039630045, 1.51521655885333e-10)
(22194.377431730372, 5.56548485339069e-10)
(38298.296037862696, 1.86910426360432e-10)
(15414.135931296803, 1.15384352525886e-9)
(31517.62830553795, 2.75984274890955e-10)
(-33929.14120716271, 2.38147527898935e-10)
(17956.6734820545, 8.50227618562664e-10)
(-30538.821127405798, 2.93958939883183e-10)
(-39014.65305203102, 1.80109666392998e-10)
(-37319.47897968401, 1.96843537773707e-10)
(41688.65026917884, 1.57745563695807e-10)
(-19520.51561248225, 7.19457645825396e-10)
(28974.898092493, 3.26548015491439e-10)
(-21215.602034471383, 6.0908490437413e-10)
(34907.954057224626, 2.249796169199e-10)
(35755.53821225075, 2.14439828003555e-10)
(30670.050038167443, 2.91448796098933e-10)
(21346.82647110723, 6.01619591580903e-10)
(7787.629828284889, 4.52025541769381e-9)
(-34776.724194877075, 2.2668072985971e-10)
(-32233.9786046248, 2.63854010515731e-10)
(-36471.89314915066, 2.06098854086382e-10)
(-22063.15234193787, 5.63188480102419e-10)
(32365.20794137646, 2.61718695088448e-10)
(25584.61684732025, 4.18824622154535e-10)
(-33081.5593147672, 2.50506920852841e-10)
(34060.37090743066, 2.36315978263408e-10)
(-14435.430725560725, 1.31560338380833e-9)
(12871.708795366323, 1.65466664580886e-9)
(-18672.980800200665, 7.86248938534151e-10)
(29822.473256721143, 3.08250470641355e-10)
(-11893.06457134755, 1.93818037748311e-9)
(-13587.956495951206, 1.48482538515329e-9)
(17109.15177130684, 9.36546862960578e-10)
(-17825.452663940443, 8.6279132465024e-10)
(-20368.056259186636, 6.60828893142411e-10)
(11176.85660268599, 2.19452935611824e-9)
(-22910.70667421052, 5.22290623488181e-10)
(-26300.956410285813, 3.96321062368272e-10)
(10329.475221035374, 2.56934772294664e-9)
(39993.471817872116, 1.71401422694693e-10)
(-28843.669685376106, 3.29526106780598e-10)
(20499.27995889174, 6.52395624457449e-10)
(-38167.06563191924, 1.88197942806359e-10)
(-7656.464461380434, 4.67645357845298e-9)
(18804.202711368536, 7.75313942157111e-10)
(-40709.830003104886, 1.65422332126805e-10)
(0, 0)
(19651.738476518363, 7.09881589730627e-10)
(39145.883572155995, 1.78904117429925e-10)
(-24605.82573604609, 4.52807764996633e-10)
(24737.052394664144, 4.48016382955832e-10)
(-9350.94656395263, 3.135208168526e-9)
(-8503.66844061373, 3.7910798424386e-9)
(-10198.279974978675, 2.63587802349588e-9)
(36603.12330229937, 2.04623693393831e-10)
(16261.63876927437, 1.03671000682342e-9)
(23041.93234561868, 5.16358643085914e-10)
(-35624.30819929549, 2.16022601467523e-10)
(-16977.93221534326, 9.51079448500519e-10)
(28127.324692714363, 3.46524414446513e-10)
(-23758.264596923887, 4.85691000942603e-10)
(-42405.009486059076, 1.52460931376032e-10)
(-31386.399173119684, 2.78296910014492e-10)
(27279.753223047952, 3.68391510353174e-10)
(13719.168393577056, 1.45655951774159e-9)
(-27148.525417319343, 3.71961477219723e-10)
(8634.84682209105, 3.67677134219538e-9)
(12024.269930847862, 1.89611415753716e-9)
(-11045.655711966832, 2.24697143936919e-9)
Intervalos de crecimiento y decrecimiento de la función:Hallemos los intervalos donde la función crece y decrece y también los puntos mínimos y máximos de la función, para lo cual miramos cómo se comporta la función en los extremos con desviación mínima del extremo:
Puntos mínimos de la función:
$$x_{1} = 0$$
La función no tiene puntos máximos
Decrece en los intervalos
$$\left[0, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, 0\right]$$