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$$2 x^{3} \cos{\left(2 x \right)} + 3 x^{2} \sin{\left(2 x \right)} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = 47.9249323344094$$
$$x_{2} = -10.2826039699167$$
$$x_{3} = 11.8439605280008$$
$$x_{4} = -1.22782193143972$$
$$x_{5} = 54.2063057730885$$
$$x_{6} = -40.0740129706512$$
$$x_{7} = 5.62802150717675$$
$$x_{8} = -44.7844359449587$$
$$x_{9} = -33.7942995608669$$
$$x_{10} = -55.7767128328603$$
$$x_{11} = -32.2245820689369$$
$$x_{12} = -76.1934639421929$$
$$x_{13} = -49.4952326320496$$
$$x_{14} = -63.6290361239317$$
$$x_{15} = 76.1934639421929$$
$$x_{16} = -19.6730037732597$$
$$x_{17} = -62.0585379193797$$
$$x_{18} = -85.6171588404973$$
$$x_{19} = -98.1824086733896$$
$$x_{20} = 62.0585379193797$$
$$x_{21} = 49.4952326320496$$
$$x_{22} = 2.6164692267562$$
$$x_{23} = -41.6441046295573$$
$$x_{24} = -60.4880551831425$$
$$x_{25} = 29.085495270014$$
$$x_{26} = -13.4074760654875$$
$$x_{27} = -57.3471411923439$$
$$x_{28} = -24.37806968342$$
$$x_{29} = -11.8439605280008$$
$$x_{30} = 84.0465261650259$$
$$x_{31} = -84.0465261650259$$
$$x_{32} = 24.37806968342$$
$$x_{33} = 4.10226568129063$$
$$x_{34} = 98.1824086733896$$
$$x_{35} = 10.2826039699167$$
$$x_{36} = 32.2245820689369$$
$$x_{37} = 0$$
$$x_{38} = 38.5039786681257$$
$$x_{39} = -82.4758997198447$$
$$x_{40} = -74.622874706927$$
$$x_{41} = 52.635921916513$$
$$x_{42} = 77.7640615384407$$
$$x_{43} = 16.5385861921536$$
$$x_{44} = 30.6549747237827$$
$$x_{45} = -1.27381931903792 \cdot 10^{-5}$$
$$x_{46} = -4.10226568129063$$
$$x_{47} = -99.7530847493478$$
$$x_{48} = -90.3290910005897$$
$$x_{49} = -91.8997454600995$$
$$x_{50} = -77.7640615384407$$
$$x_{51} = -68.3406128944097$$
$$x_{52} = -7.17167539419575$$
$$x_{53} = 85.6171588404973$$
$$x_{54} = 96.6117365061729$$
$$x_{55} = 14.9724903867582$$
$$x_{56} = 69.91116279715$$
$$x_{57} = 41.6441046295573$$
$$x_{58} = 68.3406128944097$$
$$x_{59} = -38.5039786681257$$
$$x_{60} = -71.4817235219672$$
$$x_{61} = 99.7530847493478$$
$$x_{62} = 18.1054872777926$$
$$x_{63} = -25.9470123181995$$
$$x_{64} = -69.91116279715$$
$$x_{65} = -35.3641125887692$$
$$x_{66} = 88.7584415601129$$
$$x_{67} = 46.3546655978102$$
$$x_{68} = 91.8997454600995$$
$$x_{69} = -46.3546655978102$$
$$x_{70} = 55.7767128328603$$
$$x_{71} = -79.3346669994664$$
$$x_{72} = 40.0740129706512$$
$$x_{73} = -8.72451217135942$$
$$x_{74} = 74.622874706927$$
$$x_{75} = 71.4817235219672$$
$$x_{76} = 21.2410009626834$$
$$x_{77} = 82.4758997198447$$
$$x_{78} = -18.1054872777926$$
$$x_{79} = 63.6290361239317$$
$$x_{80} = 27.5161654720774$$
$$x_{81} = 90.3290910005897$$
$$x_{82} = -27.5161654720774$$
$$x_{83} = -21.2410009626834$$
$$x_{84} = -5.62802150717675$$
$$x_{85} = 60.4880551831425$$
$$x_{86} = 33.7942995608669$$
$$x_{87} = -93.4704046857599$$
$$x_{88} = -54.2063057730885$$
$$x_{89} = 93.4704046857599$$
$$x_{90} = 19.6730037732597$$
$$x_{91} = -47.9249323344094$$
$$x_{92} = 25.9470123181995$$
Signos de extremos en los puntos:
(47.92493233440943, 110020.067366202)
(-10.28260396991667, 1075.81319367875)
(11.843960528000844, -1648.2974072075)
(-1.22782193143972, 1.17243656093029)
(54.206305773088495, 159214.719645564)
(-40.07401297065124, -64310.8840683886)
(5.628021507176746, -172.252470254656)
(-44.78443594495867, 89771.3713707053)
(-33.7942995608669, -38556.9755629467)
(-55.77671283286032, -173460.964415744)
(-32.22458206893689, 33426.5755569007)
(-76.19346394219286, 442251.191344079)
(-49.495232632049614, -121196.690834931)
(-63.62903612393173, 257540.413923442)
(76.19346394219286, 442251.191344079)
(-19.67300377325972, 7591.94906051947)
(-62.05853791937968, -238933.911571878)
(-85.61715884049732, 627502.981482316)
(-98.18240867338956, 946346.911128967)
(62.05853791937968, -238933.911571878)
(49.495232632049614, -121196.690834931)
(2.616469226756203, -15.5395850793378)
(-41.64410462955729, 72173.7118924681)
(-60.488055183142485, 221245.970153935)
(29.08549527001398, 24572.6850569784)
(-13.40747606548751, 2395.19017816037)
(-57.34714119234387, 188532.751284596)
(-24.378069683419987, -14460.3021958633)
(-11.843960528000844, -1648.2974072075)
(84.04652616502592, -593594.881702365)
(-84.04652616502592, -593594.881702365)
(24.378069683419987, -14460.3021958633)
(4.102265681290634, 64.8368741941138)
(98.18240867338956, 946346.911128967)
(10.28260396991667, 1075.81319367875)
(32.22458206893689, 33426.5755569007)
(0, 0)
(38.50397866812573, 57041.0512375873)
(-82.4758997198447, 560930.908768958)
(-74.62287470692696, -415459.032025635)
(52.63592191651302, -145770.762264945)
(77.76406153844069, -470171.203969721)
(16.538586192153595, 4505.22212782221)
(30.654974723782733, -28772.8969623597)
(-1.2738193190379192e-05, 5.26576314371066e-20)
(-4.102265681290634, 64.8368741941138)
(-99.75308474934779, -992498.614376456)
(-90.32909100058974, -736924.588979275)
(-91.89974546009948, 776041.743223149)
(-77.76406153844069, -470171.203969721)
(-68.34061289440973, -319103.833663929)
(-7.171675394195755, 361.047547551862)
(85.61715884049732, 627502.981482316)
(96.61173650617286, -901648.627097571)
(14.972490386758171, -3339.74673736232)
(69.91116279715004, 341617.126833644)
(41.64410462955729, 72173.7118924681)
(68.34061289440973, -319103.833663929)
(-38.50397866812573, 57041.0512375873)
(-71.48172352196723, -365165.254478444)
(99.75308474934779, -992498.614376456)
(18.105487277792616, -5914.87128129151)
(-25.9470123181995, 17439.6424066069)
(-69.91116279715004, 341617.126833644)
(-35.36411258876923, 44187.3517002339)
(88.75844156011291, 699144.580413006)
(46.35466559781024, -99552.7124482832)
(91.89974546009948, 776041.743223149)
(-46.35466559781024, -99552.7124482832)
(55.77671283286032, -173460.964415744)
(-79.33466699946635, 499242.324610489)
(40.07401297065124, -64310.8840683886)
(-8.724512171359422, -654.481972438707)
(74.62287470692696, -415459.032025635)
(71.48172352196723, -365165.254478444)
(21.24100096268344, -9559.71028374067)
(82.4758997198447, 560930.908768958)
(-18.105487277792616, -5914.87128129151)
(63.62903612393173, 257540.413923442)
(27.516165472077358, -20802.6851150688)
(90.32909100058974, -736924.588979275)
(-27.516165472077358, -20802.6851150688)
(-21.24100096268344, -9559.71028374067)
(-5.628021507176746, -172.252470254656)
(60.488055183142485, 221245.970153935)
(33.7942995608669, -38556.9755629467)
(-93.47040468575992, -816519.297852352)
(-54.206305773088495, 159214.719645564)
(93.47040468575992, -816519.297852352)
(19.67300377325972, 7591.94906051947)
(-47.92493233440943, 110020.067366202)
(25.9470123181995, 17439.6424066069)
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:
$$x_{1} = 11.8439605280008$$
$$x_{2} = -40.0740129706512$$
$$x_{3} = 5.62802150717675$$
$$x_{4} = -33.7942995608669$$
$$x_{5} = -55.7767128328603$$
$$x_{6} = -49.4952326320496$$
$$x_{7} = -62.0585379193797$$
$$x_{8} = 62.0585379193797$$
$$x_{9} = 49.4952326320496$$
$$x_{10} = 2.6164692267562$$
$$x_{11} = -24.37806968342$$
$$x_{12} = -11.8439605280008$$
$$x_{13} = 84.0465261650259$$
$$x_{14} = -84.0465261650259$$
$$x_{15} = 24.37806968342$$
$$x_{16} = 0$$
$$x_{17} = -74.622874706927$$
$$x_{18} = 52.635921916513$$
$$x_{19} = 77.7640615384407$$
$$x_{20} = 30.6549747237827$$
$$x_{21} = -99.7530847493478$$
$$x_{22} = -90.3290910005897$$
$$x_{23} = -77.7640615384407$$
$$x_{24} = -68.3406128944097$$
$$x_{25} = 96.6117365061729$$
$$x_{26} = 14.9724903867582$$
$$x_{27} = 68.3406128944097$$
$$x_{28} = -71.4817235219672$$
$$x_{29} = 99.7530847493478$$
$$x_{30} = 18.1054872777926$$
$$x_{31} = 46.3546655978102$$
$$x_{32} = -46.3546655978102$$
$$x_{33} = 55.7767128328603$$
$$x_{34} = 40.0740129706512$$
$$x_{35} = -8.72451217135942$$
$$x_{36} = 74.622874706927$$
$$x_{37} = 71.4817235219672$$
$$x_{38} = 21.2410009626834$$
$$x_{39} = -18.1054872777926$$
$$x_{40} = 27.5161654720774$$
$$x_{41} = 90.3290910005897$$
$$x_{42} = -27.5161654720774$$
$$x_{43} = -21.2410009626834$$
$$x_{44} = -5.62802150717675$$
$$x_{45} = 33.7942995608669$$
$$x_{46} = -93.4704046857599$$
$$x_{47} = 93.4704046857599$$
Puntos máximos de la función:
$$x_{47} = 47.9249323344094$$
$$x_{47} = -10.2826039699167$$
$$x_{47} = -1.22782193143972$$
$$x_{47} = 54.2063057730885$$
$$x_{47} = -44.7844359449587$$
$$x_{47} = -32.2245820689369$$
$$x_{47} = -76.1934639421929$$
$$x_{47} = -63.6290361239317$$
$$x_{47} = 76.1934639421929$$
$$x_{47} = -19.6730037732597$$
$$x_{47} = -85.6171588404973$$
$$x_{47} = -98.1824086733896$$
$$x_{47} = -41.6441046295573$$
$$x_{47} = -60.4880551831425$$
$$x_{47} = 29.085495270014$$
$$x_{47} = -13.4074760654875$$
$$x_{47} = -57.3471411923439$$
$$x_{47} = 4.10226568129063$$
$$x_{47} = 98.1824086733896$$
$$x_{47} = 10.2826039699167$$
$$x_{47} = 32.2245820689369$$
$$x_{47} = 38.5039786681257$$
$$x_{47} = -82.4758997198447$$
$$x_{47} = 16.5385861921536$$
$$x_{47} = -4.10226568129063$$
$$x_{47} = -91.8997454600995$$
$$x_{47} = -7.17167539419575$$
$$x_{47} = 85.6171588404973$$
$$x_{47} = 69.91116279715$$
$$x_{47} = 41.6441046295573$$
$$x_{47} = -38.5039786681257$$
$$x_{47} = -25.9470123181995$$
$$x_{47} = -69.91116279715$$
$$x_{47} = -35.3641125887692$$
$$x_{47} = 88.7584415601129$$
$$x_{47} = 91.8997454600995$$
$$x_{47} = -79.3346669994664$$
$$x_{47} = 82.4758997198447$$
$$x_{47} = 63.6290361239317$$
$$x_{47} = 60.4880551831425$$
$$x_{47} = -54.2063057730885$$
$$x_{47} = 19.6730037732597$$
$$x_{47} = -47.9249323344094$$
$$x_{47} = 25.9470123181995$$
Decrece en los intervalos
$$\left[99.7530847493478, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -99.7530847493478\right]$$