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$$\frac{21}{\left(-1 + e^{- 7 x}\right) \left(441 x^{2} + 1\right)} + \frac{7 e^{- 7 x} \operatorname{atan}{\left(21 x \right)}}{\left(-1 + e^{- 7 x}\right)^{2}} = 0$$
Resolvermos esta ecuaciónRaíces de esta ecuación
$$x_{1} = -22.8842539953742$$
$$x_{2} = -36.8842355865602$$
$$x_{3} = 425445.756830594$$
$$x_{4} = 486111.849537218$$
$$x_{5} = -18.884269098184$$
$$x_{6} = 415334.742717673$$
$$x_{7} = -84.8842270364822$$
$$x_{8} = -88.8842268697832$$
$$x_{9} = -74.8842275794177$$
$$x_{10} = -94.8842266588463$$
$$x_{11} = -60.8842288510571$$
$$x_{12} = -6.88474862240126$$
$$x_{13} = 203003.657852745$$
$$x_{14} = 334446.649820738$$
$$x_{15} = -52.8842300903987$$
$$x_{16} = -38.8842344948472$$
$$x_{17} = -90.8842267947221$$
$$x_{18} = -24.8842492156506$$
$$x_{19} = -102.884226433859$$
$$x_{20} = 496222.86610836$$
$$x_{21} = -28.8842426394062$$
$$x_{22} = -86.8842269501962$$
$$x_{23} = -70.884227865325$$
$$x_{24} = 192892.676027461$$
$$x_{25} = -56.8842294033886$$
$$x_{26} = 213114.643614267$$
$$x_{27} = 324335.6414891$$
$$x_{28} = -58.8842291127238$$
$$x_{29} = -14.884300219964$$
$$x_{30} = -66.884228205515$$
$$x_{31} = -68.8842280278203$$
$$x_{32} = -98.884226539408$$
$$x_{33} = 283891.618828076$$
$$x_{34} = -34.8842368821746$$
$$x_{35} = -80.8842272290936$$
$$x_{36} = -32.884238435862$$
$$x_{37} = 435556.771370233$$
$$x_{38} = -12.8843300187162$$
$$x_{39} = -72.8842277163435$$
$$x_{40} = -30.8842403210729$$
$$x_{41} = 233336.624899011$$
$$x_{42} = -64.8842284003657$$
$$x_{43} = -40.8842335663726$$
$$x_{44} = -54.884229727501$$
$$x_{45} = -26.8842455346378$$
$$x_{46} = -96.8842265972443$$
$$x_{47} = -48.8842309597332$$
$$x_{48} = -10.8843820856381$$
$$x_{49} = 263669.615614823$$
$$x_{50} = 273780.616420092$$
$$x_{51} = 506333.882948388$$
$$x_{52} = -78.8842273368283$$
$$x_{53} = 445667.786307546$$
$$x_{54} = 314224.634121048$$
$$x_{55} = 344557.659031129$$
$$x_{56} = -20.8842603599343$$
$$x_{57} = 455778.801616065$$
$$x_{58} = 385001.703275443$$
$$x_{59} = -46.8842314836363$$
$$x_{60} = -50.884230498528$$
$$x_{61} = 374890.691223754$$
$$x_{62} = 465889.817271621$$
$$x_{63} = 364779.679795859$$
$$x_{64} = -44.8842320821439$$
$$x_{65} = -62.8842286146548$$
$$x_{66} = 304113.627812703$$
$$x_{67} = 294002.622673405$$
$$x_{68} = 476000.833252097$$
$$x_{69} = 223225.632777091$$
$$x_{70} = 253558.61660402$$
$$x_{71} = 243447.619611292$$
$$x_{72} = -76.8842274532808$$
$$x_{73} = -92.8842267245482$$
$$x_{74} = -8.8844862363379$$
$$x_{75} = -100.884226485037$$
$$x_{76} = -4.88585631365968$$
$$x_{77} = -82.8842271292276$$
$$x_{78} = 395112.715903034$$
$$x_{79} = 405223.729063415$$
$$x_{80} = -42.8842327701303$$
$$x_{81} = -16.8842815605783$$
$$x_{82} = 354668.669045112$$
Signos de extremos en los puntos:
(-22.884253995374216, -4.22675961497869e-70)
(-36.88423558656017, -1.16258011845395e-112)
(425445.756830594, -1.57079621486747)
(486111.8495372181, -1.57079622883586)
(-18.884269098184017, -6.11061735845734e-58)
(415334.7427176733, -1.57079621214268)
(-84.88422703648223, -1.3890085822273e-258)
(-88.88422686978318, -9.60432670959798e-271)
(-74.88422757941768, -3.49378593075156e-228)
(-94.88422665884634, -5.52215631400424e-289)
(-60.88422885105709, -1.27089949298157e-185)
(-6.8847486224012595, -1.83715174050912e-21)
(203003.65785274474, -1.57079609222253)
(334446.6498207385, -1.5707961844133)
(-52.88423009039866, -2.65806560683146e-161)
(-38.88423449484723, -9.66767045643497e-119)
(-90.88422679472208, -7.98633764405346e-277)
(-24.88424921565064, -3.51516432030204e-76)
(-102.88422643385864, -2.64015354968762e-313)
(496222.86610836035, -1.57079623083187)
(-28.884242639406214, -2.43104770965539e-88)
(-86.88422695019615, -1.15501072344233e-264)
(-70.88422786532504, -5.05278699331979e-216)
(192892.67602746093, -1.5707960799268)
(-56.88422940338855, -1.83797587672084e-173)
(213114.6436142669, -1.57079610335156)
(324335.6414890997, -1.57079617997462)
(-58.88422911272382, -1.52836051505099e-179)
(-14.884300219963954, -8.83178060428663e-46)
(-66.88422820551497, -7.30742449586651e-204)
(-68.88422802782034, -6.07642088840017e-210)
(-98.884226539408, -3.81829237617182e-301)
(283891.61882807646, -1.57079615905818)
(-34.884236882174626, -1.39804521580248e-106)
(-80.88422722909364, -2.00882527354715e-246)
(-32.884238435862024, -1.68118794220592e-100)
(435556.77137023327, -1.57079621746576)
(-12.884330018716195, -1.06155579554153e-39)
(-72.88422771634355, -4.20159120707387e-222)
(-30.884240321072895, -2.02165633247495e-94)
(233336.62489901093, -1.57079612271614)
(-64.88422840036574, -8.78780518671759e-198)
(-40.88423356637257, -8.03930471162897e-125)
(-54.88422972750102, -2.21030970059969e-167)
(-26.884245534637756, -2.92330063611182e-82)
(-96.88422659724432, -4.59186384136685e-295)
(-48.88423095973321, -3.8440423484708e-149)
(-10.88438208563809, -1.27561332516909e-33)
(263669.61561482295, -1.5707961461937)
(273780.6164200921, -1.57079615286349)
(506333.88294838846, -1.57079623274816)
(-78.88422733682835, -2.41579709336053e-240)
(445667.7863075462, -1.57079621994614)
(314224.6341210483, -1.57079617525029)
(344557.6590311293, -1.57079618859147)
(-20.884260359934316, -5.08224708219519e-64)
(455778.8016160654, -1.57079622231648)
(385001.7032754429, -1.57079620310961)
(-46.88423148363634, -4.62272247372513e-143)
(-50.884230498528, -3.19651989018615e-155)
(374890.6912237538, -1.57079619977374)
(465889.8172716211, -1.57079622458393)
(364779.67979585886, -1.57079619625296)
(-44.884232082143896, -5.55912228416105e-137)
(-62.88422861465484, -1.05680791992481e-191)
(304113.6278127029, -1.57079617021182)
(294002.6226734054, -1.57079616482679)
(476000.83325209725, -1.57079622675506)
(223225.63277709106, -1.57079611347241)
(253558.61660401963, -1.57079613899198)
(243447.61961129168, -1.57079613119205)
(-76.88422745328079, -2.90521651141507e-234)
(-92.88422672454823, -6.64092008588277e-283)
(-8.884486236337901, -1.53197630850707e-27)
(-100.88422648503656, -3.17504027992865e-307)
(-4.885856313659682, -2.18833522269578e-15)
(-82.88422712922764, -1.67041218686558e-252)
(395112.715903034, -1.57079620627474)
(405223.7290634153, -1.57079620928192)
(-42.884232770130325, -6.685181352399e-131)
(-16.884281560578337, -7.34661407886626e-52)
(354668.66904511175, -1.57079619253142)
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:
La función no tiene puntos mínimos
La función no tiene puntos máximos
Decrece en todo el eje numérico