Ejercicios De Homogeneas Y No Homogeneas.docx

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Ejercicio 2 letra C. ο‚·

𝑦 ´´ βˆ’ 2𝑦 Β΄ + 5𝑦 = 𝑒 π‘₯ cos 2π‘₯ 𝑦 = 𝑦𝑐 + 𝑦𝑝 𝑦𝑐" βˆ’ 2𝑦𝑐′ + 5𝑦𝑐 = 0 π‘š2 βˆ’ 2π‘š + 5 = 0

π‘š=

βˆ’π‘ Β± βˆšπ‘ 2 βˆ’ 4π‘Žπ‘ 2π‘Ž

π‘š=

βˆ’(βˆ’2) Β± √(βˆ’2)2 βˆ’ 4(1)(5) 2(1)

π‘š=

2 Β± √4 βˆ’ 20 2

π‘š=

2 Β± βˆšβˆ’16 2

π‘š1 = 1 + 2𝑗 π‘š2 = 1 βˆ’ 2𝑗 𝑦𝑐 = 𝐢1𝑒 ∝π‘₯ cos(𝛽π‘₯) + 𝐢2 𝑒 𝛼π‘₯ 𝑠𝑒𝑛 (𝛽π‘₯) 𝑦𝑐 = 𝐢1𝑒 π‘₯ cos(2π‘₯) + 𝐢2𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) Para especificar los coeficientes podemos utilizar las letras [A y B] 𝑦𝑝 = 𝐴𝑒 π‘₯ cos(2π‘₯) + 𝐡 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) Podemos ver que los tΓ©rminos que se encontraron en yp son los mismos tΓ©rminos encontrados en yc. le agregamos un (x), a cada uno para diferenciarlos 𝑦𝑝 = 𝐴π‘₯ 𝑒 π‘₯ cos(2π‘₯) + 𝐡π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯)

Derivamos 2 veces (Yp), tomando en cuenta el grado de la ecuaciΓ³n ( y" ) 𝑦𝑝 = 𝐴π‘₯ 𝑒 π‘₯ cos(2π‘₯) + 𝐡π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) 𝑦𝑝′ = 𝐴 𝑒 π‘₯ cos(2π‘₯) + 𝐴π‘₯ 𝑒 π‘₯ cos(2π‘₯) βˆ’ 2𝐴π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 𝐡 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 𝐡π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 2𝐡π‘₯ 𝑒 π‘₯ cos(2π‘₯) 𝑦𝑝" = 𝐴 𝑒 π‘₯ cos (2π‘₯) βˆ’ 2𝐴 𝑒 π‘₯ (2π‘₯) + 𝐴 𝑒 π‘₯ cos (2π‘₯) + 𝐴π‘₯ 𝑒 π‘₯ cos (2π‘₯) βˆ’ 2𝐴π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) βˆ’ 2𝐴 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) βˆ’ 2𝐴π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) βˆ’ 4𝐴π‘₯ 𝑒 π‘₯ cos (2π‘₯) + 𝐡 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 2𝐡 𝑒 π‘₯ cos (2π‘₯) + 𝐡 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 𝐡π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 2𝐡π‘₯ 𝑒 π‘₯ cos (2π‘₯) + 2𝐡 𝑒 π‘₯ cos (2π‘₯) + 2𝐡π‘₯ 𝑒 π‘₯ cos (2π‘₯) βˆ’ 4𝐡π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) Se realiza la bΓΊsqueda de los valores de (A y B), para que [Yp] sea una SoluciΓ³n: 𝑦" βˆ’ 2𝑦′ + 5𝑦 𝑦𝑝" = 𝐴 𝑒 π‘₯ cos (2π‘₯) βˆ’ 2𝐴 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 𝐴 𝑒 π‘₯ cos (2π‘₯) + 𝐴π‘₯ 𝑒 π‘₯ cos (2π‘₯) βˆ’ 2𝐴π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) βˆ’ 2𝐴 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) βˆ’ 2𝐴π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) βˆ’ 4𝐴π‘₯ 𝑒 π‘₯ cos (2π‘₯) + 𝐡 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 2𝐡 𝑒 π‘₯ cos (2π‘₯) + 𝐡 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 𝐡π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 2𝐡π‘₯ 𝑒 π‘₯ cos (2π‘₯) + 2𝐡 𝑒 π‘₯ cos (2π‘₯) + 2𝐡π‘₯ 𝑒 π‘₯ cos (2π‘₯) βˆ’ 4𝐡π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) βˆ’2𝑦𝑝′ = βˆ’2(𝐴 𝑒 π‘₯ cos(2π‘₯) + 𝐴π‘₯ 𝑒 π‘₯ cos(2π‘₯) βˆ’ 2𝐴π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 𝐡 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 𝐡π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 2𝐡π‘₯ 𝑒 π‘₯ cos(2π‘₯)) 5𝑦𝑝 = 5(𝐴π‘₯ 𝑒 π‘₯ cos(2π‘₯) + 𝐡π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛(2π‘₯) Agrupamos tΓ©rminos: 𝐴 𝑒 π‘₯ cos(2π‘₯) + 𝐴 𝑒 π‘₯ cos(2π‘₯) + 2𝐡 𝑒 π‘₯ cos(2π‘₯) + 2𝐡 𝑒 π‘₯ cos(2π‘₯) + 2𝐡 𝑒 π‘₯ cos(2π‘₯) βˆ’ 2𝐴 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) βˆ’ 2𝐴 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 𝐡 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 𝐡 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 𝐴π‘₯ 𝑒 π‘₯ cos(2π‘₯) βˆ’ 4𝐴π‘₯ 𝑒 π‘₯ cos(2π‘₯) + 2𝐡π‘₯ 𝑒 π‘₯ cos(2π‘₯) + 2𝐡π‘₯ 𝑒 π‘₯ cos(2π‘₯) βˆ’ 2𝐴π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) βˆ’ 2𝐴π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + 𝐡π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) βˆ’ 4𝐡π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) βˆ’ 2𝐴 𝑒 π‘₯ cos(2π‘₯) βˆ’ 2𝐴π‘₯ 𝑒 π‘₯ cos(2π‘₯) βˆ’ 4𝐡π‘₯ 𝑒 π‘₯ cos(2π‘₯) + 4𝐴π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) βˆ’ 2𝐡π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) βˆ’ 2𝐡 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯)

5𝐴π‘₯ 𝑒 π‘₯ cos(2π‘₯) + 5𝐡π‘₯ 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) Realizamos la SimplificaciΓ³n de TΓ©rminos 4𝐡 𝑒 π‘₯ cos(2π‘₯) βˆ’4𝐴 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯)

Formamos las siguientes ecuaciones y las igualamos: 𝑦" βˆ’ 2𝑦′ + 5𝑦 = 𝑒 π‘₯ cos (2π‘₯) 4𝐡 𝑒 π‘₯ cos(2π‘₯) = 𝑒 π‘₯ cos(2π‘₯) 4𝐡 = 1 𝐡 = 1/4 βˆ’4𝐴 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) βˆ’4𝐴 = 0 𝐴=0 Realizamos la sustituciΓ³n de los valores encontrados de A y B en la ecuaciΓ³n de yp: 𝑦𝑝 = 𝐴 𝑒 π‘₯ cos(2π‘₯) + 𝐡 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) 1 𝑦𝑝 = ( ) 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) 4

Buscamos la Y general: 𝑦𝑑 = π‘Œπ‘ + π‘Œπ‘ 1 𝑦𝑑 = 𝐢1 𝑒 π‘₯ cos(2π‘₯) + 𝐢2 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) + ( ) 𝑒 π‘₯ 𝑠𝑒𝑛 (2π‘₯) 4

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