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$$- 4 \left(- \sin{\left(3 x \right)} - \cos{\left(3 x \right)}\right) e^{- 4 x} + \left(3 \sin{\left(3 x \right)} - 3 \cos{\left(3 x \right)}\right) e^{- 4 x} - \frac{72 \sin{\left(4 x \right)}}{1105} + \frac{256 \cos{\left(4 x \right)}}{1105} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = 5.82194436323591$$
$$x_{2} = 462.923675460016$$
$$x_{3} = 63.9414084541121$$
$$x_{4} = 26.2422966110346$$
$$x_{5} = 100.069723970395$$
$$x_{6} = 1.89327207567766$$
$$x_{7} = 40.3794635521887$$
$$x_{8} = 49.8042415129581$$
$$x_{9} = 78.0785753952662$$
$$x_{10} = 178.60954031014$$
$$x_{11} = 96.1427331534075$$
$$x_{12} = 85.9325570292407$$
$$x_{13} = 80.4347698854585$$
$$x_{14} = 52.1604360031504$$
$$x_{15} = 48.2334451861632$$
$$x_{16} = 67.8683992710994$$
$$x_{17} = 23.8861021208423$$
$$x_{18} = 66.2976029443045$$
$$x_{19} = 82.0055662122534$$
$$x_{20} = 62.3706121273172$$
$$x_{21} = 88.288751519433$$
$$x_{22} = 41.9502598789836$$
$$x_{23} = 44.3064543691759$$
$$x_{24} = 34.0962782450091$$
$$x_{25} = 70.2245937612917$$
$$x_{26} = 22.3153057940474$$
$$x_{27} = -5.28328677418757$$
$$x_{28} = 89.8595478462279$$
$$x_{29} = 84.3617607024458$$
$$x_{30} = 60.0144176371249$$
$$x_{31} = 38.0232690619963$$
$$x_{32} = 30.1692874280218$$
$$x_{33} = 12.1051296698805$$
$$x_{34} = 15.2467223234703$$
$$x_{35} = 74.151584578279$$
$$x_{36} = 92.2157423364203$$
$$x_{37} = -7.37768187657757$$
$$x_{38} = 27.8130929378295$$
$$x_{39} = 19.959111303855$$
$$x_{40} = 93.0011404998177$$
$$x_{41} = 36.4524727352014$$
$$x_{42} = 18.3883149770601$$
$$x_{43} = 71.7953900880866$$
$$x_{44} = -0.056345037008301$$
$$x_{45} = 56.0874268201376$$
$$x_{46} = 27.0276947744321$$
$$x_{47} = 45.8772506959708$$
$$x_{48} = 16.0321204868678$$
$$x_{49} = -3.18889163916542$$
$$x_{50} = 58.44362131033$$
$$x_{51} = 8.17813885289327$$
$$x_{52} = 4.2511479381124$$
Signos de extremos en los puntos:
(5.821944363235914, -0.0601656836983174)
(462.9236754600159, -0.0601656837596187)
(63.94140845411212, -0.0601656837596187)
(26.242296611034604, -0.0601656837596187)
(100.06972397039475, -0.0601656837596187)
(1.8932720756776622, 0.0600327082221495)
(40.379463552188675, -0.0601656837596187)
(49.80424151295805, -0.0601656837596187)
(78.0785753952662, -0.0601656837596187)
(178.60954031013958, -0.0601656837596187)
(96.1427331534075, 0.0601656837596187)
(85.93255702924067, -0.0601656837596187)
(80.43476988545854, 0.0601656837596187)
(52.160436003150394, 0.0601656837596187)
(48.23344518616316, -0.0601656837596187)
(67.86839927109936, 0.0601656837596187)
(23.88610212084226, 0.0601656837596187)
(66.29760294430447, 0.0601656837596187)
(82.00556621225343, 0.0601656837596187)
(62.37061212731722, -0.0601656837596187)
(88.28875151943302, 0.0601656837596187)
(41.95025987898357, -0.0601656837596187)
(44.30645436917592, 0.0601656837596187)
(34.09627824500909, -0.0601656837596187)
(70.22459376129171, -0.0601656837596187)
(22.31530579404736, 0.0601656837596187)
(-5.283286774187575, 1278425479.06325)
(89.85954784622791, 0.0601656837596187)
(84.36176070244578, -0.0601656837596187)
(60.01441763712488, 0.0601656837596187)
(38.02326906199633, 0.0601656837596187)
(30.169287428021846, 0.0601656837596187)
(12.105129669880535, -0.0601656837596187)
(15.246722323470328, -0.0601656837596187)
(74.15158457827896, 0.0601656837596187)
(92.21574233642026, -0.0601656837596187)
(-7.377681876577573, 5559200799845.24)
(27.8130929378295, -0.0601656837596187)
(19.959111303855018, -0.0601656837596187)
(93.00114049981771, 0.0601656837596187)
(36.45247273520143, 0.0601656837596187)
(18.38831497706012, -0.0601656837596187)
(71.7953900880866, -0.0601656837596187)
(-0.05634503700830103, -1.02124929304961)
(56.08742682013764, -0.0601656837596187)
(27.027694774432053, 0.0601656837596187)
(45.87725069597081, 0.0601656837596187)
(16.032120486867775, 0.0601656837596187)
(-3.188891639165417, 293994.009730565)
(58.44362131032999, 0.0601656837596187)
(8.178138852893273, 0.0601656837596171)
(4.251147938112403, -0.0601657319146828)
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:
$$x_{1} = 5.82194436323591$$
$$x_{2} = 462.923675460016$$
$$x_{3} = 63.9414084541121$$
$$x_{4} = 26.2422966110346$$
$$x_{5} = 100.069723970395$$
$$x_{6} = 40.3794635521887$$
$$x_{7} = 49.8042415129581$$
$$x_{8} = 78.0785753952662$$
$$x_{9} = 178.60954031014$$
$$x_{10} = 85.9325570292407$$
$$x_{11} = 48.2334451861632$$
$$x_{12} = 62.3706121273172$$
$$x_{13} = 41.9502598789836$$
$$x_{14} = 34.0962782450091$$
$$x_{15} = 70.2245937612917$$
$$x_{16} = 84.3617607024458$$
$$x_{17} = 12.1051296698805$$
$$x_{18} = 15.2467223234703$$
$$x_{19} = 92.2157423364203$$
$$x_{20} = 27.8130929378295$$
$$x_{21} = 19.959111303855$$
$$x_{22} = 18.3883149770601$$
$$x_{23} = 71.7953900880866$$
$$x_{24} = -0.056345037008301$$
$$x_{25} = 56.0874268201376$$
$$x_{26} = 4.2511479381124$$
Puntos máximos de la función:
$$x_{26} = 1.89327207567766$$
$$x_{26} = 96.1427331534075$$
$$x_{26} = 80.4347698854585$$
$$x_{26} = 52.1604360031504$$
$$x_{26} = 67.8683992710994$$
$$x_{26} = 23.8861021208423$$
$$x_{26} = 66.2976029443045$$
$$x_{26} = 82.0055662122534$$
$$x_{26} = 88.288751519433$$
$$x_{26} = 44.3064543691759$$
$$x_{26} = 22.3153057940474$$
$$x_{26} = -5.28328677418757$$
$$x_{26} = 89.8595478462279$$
$$x_{26} = 60.0144176371249$$
$$x_{26} = 38.0232690619963$$
$$x_{26} = 30.1692874280218$$
$$x_{26} = 74.151584578279$$
$$x_{26} = -7.37768187657757$$
$$x_{26} = 93.0011404998177$$
$$x_{26} = 36.4524727352014$$
$$x_{26} = 27.0276947744321$$
$$x_{26} = 45.8772506959708$$
$$x_{26} = 16.0321204868678$$
$$x_{26} = -3.18889163916542$$
$$x_{26} = 58.44362131033$$
$$x_{26} = 8.17813885289327$$
Decrece en los intervalos
$$\left[462.923675460016, \infty\right)$$
Crece en los intervalos
$$\left(-\infty, -0.056345037008301\right]$$