Pregunta
upstudy study bank question image url

Find the general solution to the differential equation Put the problem in standard form. \( x^{2}-3 x y+x \frac{d y}{d x}=0 \) Find the integrating factor, \( \rho(x)= \) Find \( y(x)= \) Use \( C \) as the unknown constant.

Ask by John Floyd. in the United States
Mar 20,2025

Solución de inteligencia artificial de Upstudy

Respuesta verificada por el tutor

Responder

The general solution to the differential equation is \( y(x) = \frac{x}{3} + \frac{1}{9} + C e^{3x} \), where \( C \) is the constant of integration.

Solución

We start with the differential equation \[ x^{2} - 3xy + x\frac{dy}{dx} = 0. \] **Step 1. Put the equation in standard form** Since \(x \neq 0\), we can divide the entire equation by \(x\): \[ \frac{x^{2}}{x} - 3y + \frac{dy}{dx} = 0 \quad \Longrightarrow \quad x - 3y + \frac{dy}{dx} = 0. \] Rearrange to isolate \(\frac{dy}{dx}\): \[ \frac{dy}{dx} = 3y - x. \] Write this in standard linear form: \[ \frac{dy}{dx} - 3y = -x. \] Here, the coefficient function (in the standard linear form \(\frac{dy}{dx} + p(x)y = q(x)\)) is \[ p(x) = -3. \] --- **Step 2. Find the integrating factor, \(\rho(x)\)** The integrating factor is given by \[ \rho(x)= e^{\int p(x) \, dx} = e^{\int -3 \, dx} = e^{-3x}. \] Thus, \[ \rho(x) = e^{-3x}. \] --- **Step 3. Solve the differential equation** Multiply the standard form by the integrating factor: \[ e^{-3x}\frac{dy}{dx} - 3e^{-3x}y = -x e^{-3x}. \] Notice that the left-hand side is the derivative of \(\left(e^{-3x}y\right)\): \[ \frac{d}{dx}\left(e^{-3x}y\right) = -x e^{-3x}. \] Now integrate both sides with respect to \(x\): \[ \int \frac{d}{dx}\left(e^{-3x}y\right) \, dx = \int -x e^{-3x} \, dx. \] This gives \[ e^{-3x}y = \int -x e^{-3x} \, dx. \] **Step 3a. Evaluate the integral \(\int -x e^{-3x} \, dx\)** Let \[ I = \int -x e^{-3x} \, dx. \] Use integration by parts where \[ u = -x, \quad dv = e^{-3x}dx. \] Then \[ du = -dx, \quad v = \int e^{-3x}dx = -\frac{1}{3}e^{-3x}. \] Now, applying integration by parts: \[ I = u v - \int v\,du = \left(-x\right)\left(-\frac{1}{3}e^{-3x}\right) - \int \left(-\frac{1}{3}e^{-3x}\right)(-dx). \] Simplify the terms: \[ I = \frac{x}{3}e^{-3x} - \int \frac{1}{3}e^{-3x}\,dx. \] Now, integrate the remaining integral: \[ \int e^{-3x}\,dx = -\frac{1}{3}e^{-3x}. \] Thus, \[ I = \frac{x}{3}e^{-3x} - \frac{1}{3}\left(-\frac{1}{3}e^{-3x}\right) = \frac{x}{3}e^{-3x} + \frac{1}{9}e^{-3x}. \] So we have \[ e^{-3x}y = e^{-3x}\left(\frac{x}{3} + \frac{1}{9}\right) + C, \] where \(C\) is the constant of integration. --- **Step 4. Solve for \(y\)** Multiply both sides of the equation by \(e^{3x}\) to solve for \(y\): \[ y = \frac{x}{3} + \frac{1}{9} + C e^{3x}. \] --- **Final Answers** 1. The standard form of the differential equation is \[ \frac{dy}{dx} - 3y = -x. \] 2. The integrating factor is \[ \rho(x)= e^{-3x}. \] 3. The general solution is \[ y(x)= \frac{x}{3} + \frac{1}{9} + C e^{3x}. \]

Respondido por UpStudy AI y revisado por un tutor profesional

error msg
Explicar
Simplifique esta solución

Bonus Knowledge

To put the differential equation in standard form, we will first rearrange it. Start with: \[ x^2 - 3xy + x \frac{dy}{dx} = 0 \] This can be rewritten as: \[ x \frac{dy}{dx} = 3xy - x^2 \] Now, divide through by \( x \) (assuming \( x \neq 0 \)): \[ \frac{dy}{dx} = 3y - x \] Next, we have the first-order linear differential equation in standard form: \[ \frac{dy}{dx} - 3y = -x \] To find the integrating factor, \( \rho(x) \), we use the formula: \[ \rho(x) = e^{\int -3 \, dx} = e^{-3x} \] Now, multiplying both sides of the equation by the integrating factor: \[ e^{-3x} \frac{dy}{dx} - 3e^{-3x}y = -xe^{-3x} \] The left-hand side can be recognized as the derivative of \( e^{-3x}y \): \[ \frac{d}{dx}(e^{-3x}y) = -xe^{-3x} \] Integrating both sides with respect to \( x \): \[ e^{-3x}y = \int -xe^{-3x} \, dx \] This integral can be tackled using integration by parts. Let \( u = x \) and \( dv = e^{-3x}dx \): Then \( du = dx \) and \( v = -\frac{1}{3}e^{-3x} \). Applying integration by parts: \[ \int -xe^{-3x} \, dx = -\frac{x}{3}e^{-3x} - \int -\frac{1}{3}e^{-3x} \, dx \] \[ = -\frac{x}{3}e^{-3x} + \frac{1}{9}e^{-3x} + C \] Thus: \[ e^{-3x}y = -\frac{x}{3}e^{-3x} + \frac{1}{9}e^{-3x} + C \] Now multiplying through by \( e^{3x} \): \[ y = -\frac{x}{3} + \frac{1}{9} + Ce^{3x} \] So the general solution for \( y(x) \) is: \[ y(x) = -\frac{x}{3} + \frac{1}{9} + Ce^{3x} \] Teamwork makes the dream work! Get ready to solve some diff equations! For those intrigued about how history and real-life connect with differential equations, you're in for a treat!

preguntas relacionadas

Latest Calculus Questions

¡Prueba Premium ahora!
¡Prueba Premium y hazle a Thoth AI preguntas de matemáticas ilimitadas ahora!
Quizas mas tarde Hazte Premium
Estudiar puede ser una verdadera lucha
¿Por qué no estudiarlo en UpStudy?
Seleccione su plan a continuación
Prima

Puedes disfrutar

Empieza ahora
  • Explicaciones paso a paso
  • Tutores expertos en vivo 24/7
  • Número ilimitado de preguntas
  • Sin interrupciones
  • Acceso completo a Respuesta y Solución
  • Acceso completo al chat de PDF, al chat de UpStudy y al chat de navegación
Básico

Totalmente gratis pero limitado

  • Solución limitada
Bienvenido a ¡Estudia ahora!
Inicie sesión para continuar con el recorrido de Thoth AI Chat
Continuar con correo electrónico
O continuar con
Al hacer clic en "Iniciar sesión", acepta nuestros términos y condiciones. Términos de Uso & Política de privacidad