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$$- 5 \cos{\left(x \right)} + 3 - \frac{4}{x} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = 8659.15676399116$$
$$x_{2} = 99.593666256374$$
$$x_{3} = -74.4844227888752$$
$$x_{4} = -101.448366030563$$
$$x_{5} = 19.8263891583539$$
$$x_{6} = -43.0784232507229$$
$$x_{7} = -63.7433663282863$$
$$x_{8} = 32.3737658845994$$
$$x_{9} = -36.7992772881958$$
$$x_{10} = 38.6520354336436$$
$$x_{11} = -55.6394691921915$$
$$x_{12} = 5.17398805428147$$
$$x_{13} = -19.7251283309285$$
$$x_{14} = -44.8871230552348$$
$$x_{15} = 26.0978273148013$$
$$x_{16} = 68.1731539284796$$
$$x_{17} = -87.0488370640837$$
$$x_{18} = 13.5655092601862$$
$$x_{19} = 76.3385550865966$$
$$x_{20} = -24.2473585373772$$
$$x_{21} = -38.600240762574$$
$$x_{22} = 57.4932451903028$$
$$x_{23} = 61.8884958151393$$
$$x_{24} = -68.2024874381788$$
$$x_{25} = 82.6207535550359$$
$$x_{26} = 87.0258570893134$$
$$x_{27} = 43.0319604346148$$
$$x_{28} = -88.8805903515249$$
$$x_{29} = -70.0279757928347$$
$$x_{30} = -49.358604874442$$
$$x_{31} = 95.1855397465583$$
$$x_{32} = -95.164524774114$$
$$x_{33} = -82.5965413923539$$
$$x_{34} = 1.50300976346137$$
$$x_{35} = -30.5218137237599$$
$$x_{36} = 88.9030909044499$$
$$x_{37} = -7.05976001620841$$
$$x_{38} = -17.9791235997861$$
$$x_{39} = -80.7665534881257$$
$$x_{40} = -32.311900428637$$
$$x_{41} = 17.8673939120046$$
$$x_{42} = -26.0210254679911$$
$$x_{43} = 51.2121645607065$$
$$x_{44} = 80.7417852981937$$
$$x_{45} = 30.4561862941834$$
$$x_{46} = -13.4168451851825$$
$$x_{47} = 70.056532656695$$
$$x_{48} = -51.1730895286278$$
$$x_{49} = 55.603506810047$$
$$x_{50} = -93.331242524074$$
$$x_{51} = 49.3180612245419$$
$$x_{52} = 44.931667445655$$
$$x_{53} = -57.4584431018328$$
$$x_{54} = 24.1646752551122$$
$$x_{55} = 36.7448709415722$$
$$x_{56} = 93.3098099288294$$
$$x_{57} = 63.7747379736411$$
$$x_{58} = -5.55158029993605$$
$$x_{59} = -76.3123494474998$$
$$x_{60} = -61.9208072429477$$
$$x_{61} = 7.34072265652191$$
$$x_{62} = -11.7273830842277$$
$$x_{63} = -99.6137467221083$$
$$x_{64} = 11.5550788546483$$
$$x_{65} = 74.4575645731811$$
Signos de extremos en los puntos:
(8659.156763991157, 25937.2044550593)
(99.59366625637401, 284.406414171067)
(-74.48442278887525, -244.654782498991 - 4*pi*I)
(-101.44836603056332, -318.853175539216 - 4*pi*I)
(19.826389158353894, 43.3874658772698)
(-43.07842325072291, -148.2160041589 - 4*pi*I)
(-63.7433663282863, -203.897401518402 - 4*pi*I)
(32.373765884599386, 79.1221516522013)
(-36.799277288195846, -128.735864971748 - 4*pi*I)
(38.65203543364358, 97.262145407066)
(-55.63946919219154, -186.93903695161 - 4*pi*I)
(5.173988054281468, 13.4240962948854)
(-19.725128330928538, -67.2634070381814 - 4*pi*I)
(-44.88712305523475, -145.946384978343 - 4*pi*I)
(26.097827314801343, 61.1355840183632)
(68.17315392847964, 191.674598846685)
(-87.04883706408371, -282.977508995339 - 4*pi*I)
(13.565509260186223, 26.0613794247474)
(76.33855508659659, 207.636185220272)
(-24.247358537377245, -89.3660927770684 - 4*pi*I)
(-38.60024076257399, -126.493615553358 - 4*pi*I)
(57.49324519030283, 152.221818999426)
(61.88849581513934, 173.211818277258)
(-68.20248743817879, -225.452720453556 - 4*pi*I)
(82.62075355503595, 226.169360267915)
(87.02585708931342, 247.246813533313)
(43.03196043461475, 118.116165484073)
(-88.88059035152487, -280.625098323609 - 4*pi*I)
(-70.0279757928347, -223.122990862607 - 4*pi*I)
(-49.358604874441994, -167.610180703007 - 4*pi*I)
(95.18553974655828, 263.302131929885)
(-95.16452477411396, -299.747875428763 - 4*pi*I)
(-82.59654139235393, -261.482278830599 - 4*pi*I)
(1.503009763461372, -2.10936598923885)
(-30.521813723759905, -109.137476806866 - 4*pi*I)
(88.9030909044499, 244.72573255676)
(-7.059760016208413, -25.4927232212381 - 4*pi*I)
(-17.979123599786057, -69.3172541292041 - 4*pi*I)
(-80.76655348812574, -263.828284550978 - 4*pi*I)
(-32.311900428637024, -106.933354176166 - 4*pi*I)
(17.867393912004644, 46.2287703886753)
(-26.021025467991123, -87.2187425170716 - 4*pi*I)
(51.212164560706455, 133.835179977029)
(80.74178529819368, 228.69701150275)
(30.456186294183357, 81.7986151594691)
(-13.416845185182497, -46.8786119925272 - 4*pi*I)
(70.05653265669497, 189.130195340137)
(-51.17308952862778, -165.319959626718 - 4*pi*I)
(55.60350681004703, 154.790491350987)
(-93.33124252407403, -302.105841969844 - 4*pi*I)
(49.318061224541914, 136.420586087109)
(44.93166744565501, 115.509185723959)
(-57.458443101832806, -184.632747967188 - 4*pi*I)
(24.164675255112222, 63.8734126345027)
(36.744870941572245, 99.8979934426889)
(93.30980992882942, 265.817523689837)
(63.77473797364106, 170.656504208801)
(-5.551580299936049, -26.8513953329272 - 4*pi*I)
(-76.31234944749977, -242.316241550732 - 4*pi*I)
(-61.920807242947724, -206.216572697207 - 4*pi*I)
(7.340722656521914, 9.69267421445369)
(-11.727383084227696, -48.749690182 - 4*pi*I)
(-99.61374672210832, -321.216007208559 - 4*pi*I)
(11.555078854648341, 29.1143271627237)
(74.45756457318113, 210.171509588833)
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:
$$x_{1} = -74.4844227888752$$
$$x_{2} = 19.8263891583539$$
$$x_{3} = -43.0784232507229$$
$$x_{4} = 32.3737658845994$$
$$x_{5} = -36.7992772881958$$
$$x_{6} = 38.6520354336436$$
$$x_{7} = -55.6394691921915$$
$$x_{8} = 26.0978273148013$$
$$x_{9} = -87.0488370640837$$
$$x_{10} = 13.5655092601862$$
$$x_{11} = 76.3385550865966$$
$$x_{12} = -24.2473585373772$$
$$x_{13} = 57.4932451903028$$
$$x_{14} = -68.2024874381788$$
$$x_{15} = 82.6207535550359$$
$$x_{16} = -49.358604874442$$
$$x_{17} = 95.1855397465583$$
$$x_{18} = 1.50300976346137$$
$$x_{19} = -30.5218137237599$$
$$x_{20} = 88.9030909044499$$
$$x_{21} = -17.9791235997861$$
$$x_{22} = -80.7665534881257$$
$$x_{23} = 51.2121645607065$$
$$x_{24} = 70.056532656695$$
$$x_{25} = -93.331242524074$$
$$x_{26} = 44.931667445655$$
$$x_{27} = 63.7747379736411$$
$$x_{28} = -5.55158029993605$$
$$x_{29} = -61.9208072429477$$
$$x_{30} = 7.34072265652191$$
$$x_{31} = -11.7273830842277$$
$$x_{32} = -99.6137467221083$$
Puntos máximos de la función:
$$x_{32} = 99.593666256374$$
$$x_{32} = -101.448366030563$$
$$x_{32} = -63.7433663282863$$
$$x_{32} = 5.17398805428147$$
$$x_{32} = -19.7251283309285$$
$$x_{32} = -44.8871230552348$$
$$x_{32} = 68.1731539284796$$
$$x_{32} = -38.600240762574$$
$$x_{32} = 61.8884958151393$$
$$x_{32} = 87.0258570893134$$
$$x_{32} = 43.0319604346148$$
$$x_{32} = -88.8805903515249$$
$$x_{32} = -70.0279757928347$$
$$x_{32} = -95.164524774114$$
$$x_{32} = -82.5965413923539$$
$$x_{32} = -7.05976001620841$$
$$x_{32} = -32.311900428637$$
$$x_{32} = 17.8673939120046$$
$$x_{32} = -26.0210254679911$$
$$x_{32} = 80.7417852981937$$
$$x_{32} = 30.4561862941834$$
$$x_{32} = -13.4168451851825$$
$$x_{32} = -51.1730895286278$$
$$x_{32} = 55.603506810047$$
$$x_{32} = 49.3180612245419$$
$$x_{32} = -57.4584431018328$$
$$x_{32} = 24.1646752551122$$
$$x_{32} = 36.7448709415722$$
$$x_{32} = 93.3098099288294$$
$$x_{32} = -76.3123494474998$$
$$x_{32} = 11.5550788546483$$
$$x_{32} = 74.4575645731811$$
Decrece en los intervalos
$$\left[95.1855397465583, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -99.6137467221083\right]$$