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$$\frac{3 \cos{\left(3 x \right)}}{x + 1} - \frac{\sin{\left(3 x \right)}}{\left(x + 1\right)^{2}} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = 14.12982428225$$
$$x_{2} = 69.6370641802769$$
$$x_{3} = 179.5937647765$$
$$x_{4} = -9.93594832767298$$
$$x_{5} = -95.8174040963179$$
$$x_{6} = 18.3202066852905$$
$$x_{7} = 49.7396938871393$$
$$x_{8} = -24.6044355527668$$
$$x_{9} = -93.7229825247348$$
$$x_{10} = 88.486951435902$$
$$x_{11} = -45.5505994805837$$
$$x_{12} = 31.9361518962252$$
$$x_{13} = 5.74312223880499$$
$$x_{14} = -91.628559729748$$
$$x_{15} = -58.1175188064609$$
$$x_{16} = 64.4009504913397$$
$$x_{17} = 22.5100215504388$$
$$x_{18} = 12.0342491462211$$
$$x_{19} = -47.645106567098$$
$$x_{20} = -69.6370183453616$$
$$x_{21} = 73.8259424415296$$
$$x_{22} = -23.5570194717481$$
$$x_{23} = -16.2242649187407$$
$$x_{24} = 7.84142047231292$$
$$x_{25} = 4.69289372907331$$
$$x_{26} = -43.456081344904$$
$$x_{27} = -27.7465811044205$$
$$x_{28} = 78.014811366371$$
$$x_{29} = 80.1092427796838$$
$$x_{30} = 9.93822181935234$$
$$x_{31} = 93.7230078261383$$
$$x_{32} = 62.306499182809$$
$$x_{33} = 60.2120440279396$$
$$x_{34} = -39.2670046684891$$
$$x_{35} = -80.1092081466848$$
$$x_{36} = -62.3064419252179$$
$$x_{37} = -7.83774481582612$$
$$x_{38} = 86.3925265769919$$
$$x_{39} = -56.0230496579819$$
$$x_{40} = 84.2981002567875$$
$$x_{41} = -67.5425722913355$$
$$x_{42} = 58.1175846179118$$
$$x_{43} = 51.8341757962461$$
$$x_{44} = 63.3537252943945$$
$$x_{45} = -98.9590343314678$$
$$x_{46} = -25.651833064005$$
$$x_{47} = 82.2036723649355$$
$$x_{48} = -53.9285746492485$$
$$x_{49} = 91.6285862011761$$
$$x_{50} = 20.4151642358618$$
$$x_{51} = -84.2980689806444$$
$$x_{52} = 44.5034541524614$$
$$x_{53} = 100.006266101505$$
$$x_{54} = 53.9286510853179$$
$$x_{55} = -78.014774848544$$
$$x_{56} = -100.00624387984$$
$$x_{57} = -37.1724414482659$$
$$x_{58} = 42.4089412372547$$
$$x_{59} = -97.9118245238171$$
$$x_{60} = 29.8415277032178$$
$$x_{61} = 34.0307486929881$$
$$x_{62} = -71.7314613819081$$
$$x_{63} = 177.499362455113$$
$$x_{64} = -14.1287055399409$$
$$x_{65} = -51.8340930558757$$
$$x_{66} = -31.9359337983987$$
$$x_{67} = -5.73616500915147$$
$$x_{68} = -21.4621201918935$$
$$x_{69} = -65.4481229256372$$
$$x_{70} = 45.5507066343995$$
$$x_{71} = 66.4953983116055$$
$$x_{72} = -3.62305788140841$$
$$x_{73} = 2.58710744929556$$
$$x_{74} = -49.7396040289555$$
$$x_{75} = -36.1251523193003$$
$$x_{76} = 56.0231204838396$$
$$x_{77} = -60.2119827165731$$
$$x_{78} = 71.7315045787782$$
$$x_{79} = -29.8412778775691$$
$$x_{80} = 75.9203779756689$$
$$x_{81} = 27.7468701248449$$
$$x_{82} = 0.448187974568336$$
$$x_{83} = 16.2251123181467$$
$$x_{84} = 110.478344948428$$
$$x_{85} = -38.2197254236114$$
$$x_{86} = 36.1253227308377$$
$$x_{87} = -75.920339414842$$
$$x_{88} = -82.2036394745098$$
$$x_{89} = -12.0327038334478$$
$$x_{90} = -89.5341356245317$$
$$x_{91} = 38.2198776563487$$
$$x_{92} = -34.0305566395323$$
$$x_{93} = 95.8174283035917$$
$$x_{94} = 40.3144163765257$$
$$x_{95} = 97.9118477064309$$
$$x_{96} = -73.8259016613234$$
Signos de extremos en los puntos:
(14.129824282249995, -0.0660785859293905)
(69.6370641802769, 0.0141567161306691)
(179.59376477650014, -0.0055372803032317)
(-9.935948327672982, -0.111829763315158)
(-95.8174040963179, -0.0105465218133308)
(18.320206685290483, -0.0517515787945532)
(49.739693887139325, -0.0197080105350686)
(-24.604435552766752, -0.042360695400749)
(-93.72298252473482, -0.010784743016736)
(88.48695143590199, 0.0111747360530819)
(-45.550599480583735, -0.0224457587935188)
(31.936151896225223, 0.030360219187112)
(5.7431222388049905, -0.148118391509219)
(-91.62855972974802, -0.0110339747111516)
(-58.117518806460915, -0.017507465176066)
(64.40095049133973, -0.0152900990616982)
(22.510021550438797, -0.0425307777872729)
(12.03424914622112, -0.0766958758648147)
(-47.64510656709805, -0.0214379286656257)
(-69.63701834536155, 0.0145692256407006)
(73.82594244152962, 0.0133642162727651)
(-23.557019471748077, 0.044327258477468)
(-16.224264918740683, -0.0656688778583648)
(7.841420472312918, -0.113023700730784)
(4.692893729073307, 0.175357251208795)
(-43.456081344903964, -0.0235530258252866)
(-27.746581104420496, 0.0373850529267117)
(78.01481136637098, 0.0126557424419034)
(80.10924277968377, 0.0123289469989649)
(9.938221819352341, -0.0913801166102524)
(93.72300782613831, -0.0105570318258734)
(62.306499182808956, -0.0157959475099208)
(60.212044027939584, -0.0163364120443059)
(-39.26700466848911, -0.0261311820055257)
(-80.10920814668478, 0.012640641290668)
(-62.30644192521788, -0.0163112584507456)
(-7.837744815826117, -0.146073582339057)
(86.39252657699186, 0.0114425428026098)
(-56.02304965798188, -0.0181738681631)
(84.29810025678752, 0.0117235010085618)
(-67.54257229133549, 0.0150277847569876)
(58.117584617911824, -0.0169151718665832)
(51.83417579624613, -0.0189267663114366)
(63.353725294394486, 0.0155389075150156)
(-98.95903433146782, 0.0102082897959223)
(-25.65183306400502, 0.0405612269277101)
(82.2036723649355, 0.0120186038274543)
(-53.928574649248546, -0.0188930114990488)
(91.62858620117612, -0.0107957334350981)
(20.415164235861834, -0.0466902271587645)
(-84.29806898064436, 0.0120049840957714)
(44.503454152461394, 0.0219757640070935)
(100.00626610150478, -0.00990032196246201)
(53.928651085317924, -0.0182051000258538)
(-78.01477484854398, 0.0129843998837079)
(-100.00624387984038, -0.0101003158307968)
(-37.1724414482659, -0.0276441816881482)
(42.40894123725466, 0.023036049486037)
(-97.91182452381713, -0.0103185972372766)
(29.84152770321778, 0.0324219217988084)
(34.03074869298807, 0.0285450573707282)
(-71.7314613819081, 0.0141378231986919)
(177.4993624551129, -0.00560225113760133)
(-14.128705539940947, -0.0761444329268425)
(-51.83409305587572, -0.0196714142345349)
(-31.935933798398665, 0.0323229924698383)
(-5.736165009151465, -0.210620292752524)
(-21.462120191893526, 0.0488643078371435)
(-65.4481229256372, 0.0155161481741978)
(45.55070663439951, -0.021481400301457)
(66.49539831160548, -0.0148156441818527)
(-3.623057881408405, -0.378192977072814)
(2.587107449295564, 0.277580254565647)
(-49.73960402895555, -0.020516716012288)
(-36.12515231930032, 0.0284683455627401)
(56.02312048383959, -0.0175364467349013)
(-60.2119827165731, -0.0168882058818706)
(71.73150457877824, 0.013749055566867)
(-29.84127787756907, 0.0346702120109205)
(75.92037797566888, 0.0130003340714315)
(27.74687012484495, 0.0347840573609868)
(0.4481879745683365, 0.672922595004931)
(16.22511231814671, -0.05804390659776)
(110.4783449484283, -0.00897031194795463)
(-38.21972542361144, 0.0268663964506462)
(36.1253227308377, 0.0269347071291292)
(-75.92033941484198, 0.0133473781672643)
(-82.20363947450976, 0.0123146152247573)
(-12.032703833447838, -0.090598271146977)
(-89.53413562453174, -0.0112949983112211)
(38.21987765634874, 0.0254963540029187)
(-34.030556639532286, 0.0302734553929573)
(95.81742830359167, -0.0103286576680711)
(40.31441637652569, 0.0242038383037982)
(97.91184770643095, -0.01010995492221)
(-73.82590166132336, 0.0137312343865441)
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:
$$x_{1} = 14.12982428225$$
$$x_{2} = 179.5937647765$$
$$x_{3} = -9.93594832767298$$
$$x_{4} = -95.8174040963179$$
$$x_{5} = 18.3202066852905$$
$$x_{6} = 49.7396938871393$$
$$x_{7} = -24.6044355527668$$
$$x_{8} = -93.7229825247348$$
$$x_{9} = -45.5505994805837$$
$$x_{10} = 5.74312223880499$$
$$x_{11} = -91.628559729748$$
$$x_{12} = -58.1175188064609$$
$$x_{13} = 64.4009504913397$$
$$x_{14} = 22.5100215504388$$
$$x_{15} = 12.0342491462211$$
$$x_{16} = -47.645106567098$$
$$x_{17} = -16.2242649187407$$
$$x_{18} = 7.84142047231292$$
$$x_{19} = -43.456081344904$$
$$x_{20} = 9.93822181935234$$
$$x_{21} = 93.7230078261383$$
$$x_{22} = 62.306499182809$$
$$x_{23} = 60.2120440279396$$
$$x_{24} = -39.2670046684891$$
$$x_{25} = -62.3064419252179$$
$$x_{26} = -7.83774481582612$$
$$x_{27} = -56.0230496579819$$
$$x_{28} = 58.1175846179118$$
$$x_{29} = 51.8341757962461$$
$$x_{30} = -53.9285746492485$$
$$x_{31} = 91.6285862011761$$
$$x_{32} = 20.4151642358618$$
$$x_{33} = 100.006266101505$$
$$x_{34} = 53.9286510853179$$
$$x_{35} = -100.00624387984$$
$$x_{36} = -37.1724414482659$$
$$x_{37} = -97.9118245238171$$
$$x_{38} = 177.499362455113$$
$$x_{39} = -14.1287055399409$$
$$x_{40} = -51.8340930558757$$
$$x_{41} = -5.73616500915147$$
$$x_{42} = 45.5507066343995$$
$$x_{43} = 66.4953983116055$$
$$x_{44} = -3.62305788140841$$
$$x_{45} = -49.7396040289555$$
$$x_{46} = 56.0231204838396$$
$$x_{47} = -60.2119827165731$$
$$x_{48} = 16.2251123181467$$
$$x_{49} = 110.478344948428$$
$$x_{50} = -12.0327038334478$$
$$x_{51} = -89.5341356245317$$
$$x_{52} = 95.8174283035917$$
$$x_{53} = 97.9118477064309$$
Puntos máximos de la función:
$$x_{53} = 69.6370641802769$$
$$x_{53} = 88.486951435902$$
$$x_{53} = 31.9361518962252$$
$$x_{53} = -69.6370183453616$$
$$x_{53} = 73.8259424415296$$
$$x_{53} = -23.5570194717481$$
$$x_{53} = 4.69289372907331$$
$$x_{53} = -27.7465811044205$$
$$x_{53} = 78.014811366371$$
$$x_{53} = 80.1092427796838$$
$$x_{53} = -80.1092081466848$$
$$x_{53} = 86.3925265769919$$
$$x_{53} = 84.2981002567875$$
$$x_{53} = -67.5425722913355$$
$$x_{53} = 63.3537252943945$$
$$x_{53} = -98.9590343314678$$
$$x_{53} = -25.651833064005$$
$$x_{53} = 82.2036723649355$$
$$x_{53} = -84.2980689806444$$
$$x_{53} = 44.5034541524614$$
$$x_{53} = -78.014774848544$$
$$x_{53} = 42.4089412372547$$
$$x_{53} = 29.8415277032178$$
$$x_{53} = 34.0307486929881$$
$$x_{53} = -71.7314613819081$$
$$x_{53} = -31.9359337983987$$
$$x_{53} = -21.4621201918935$$
$$x_{53} = -65.4481229256372$$
$$x_{53} = 2.58710744929556$$
$$x_{53} = -36.1251523193003$$
$$x_{53} = 71.7315045787782$$
$$x_{53} = -29.8412778775691$$
$$x_{53} = 75.9203779756689$$
$$x_{53} = 27.7468701248449$$
$$x_{53} = 0.448187974568336$$
$$x_{53} = -38.2197254236114$$
$$x_{53} = 36.1253227308377$$
$$x_{53} = -75.920339414842$$
$$x_{53} = -82.2036394745098$$
$$x_{53} = 38.2198776563487$$
$$x_{53} = -34.0305566395323$$
$$x_{53} = 40.3144163765257$$
$$x_{53} = -73.8259016613234$$
Decrece en los intervalos
$$\left[179.5937647765, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -100.00624387984\right]$$