Solve y" +10y' +24y = 0

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
Problem 1RQ
Question
### Solving Second-Order Linear Homogeneous Differential Equations

In this module, we'll work through solving a second-order linear homogeneous differential equation. Consider the equation given below:

\[ y'' + 10y' + 24y = 0 \]

To solve this, we'll follow these steps:

1. **Characteristic Equation**: The first step is to form the characteristic (or auxiliary) equation by replacing \( y \) with \( e^{rt} \). This gives:
\[ r^2 + 10r + 24 = 0 \]

2. **Solve the Characteristic Equation**: Solve for \( r \) using the quadratic formula \( r = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \). Here, \( a = 1 \), \( b = 10 \), and \( c = 24 \).

\[ r = \frac{-10 \pm \sqrt{(10)^2 - 4(1)(24)}}{2(1)} \]
\[ = \frac{-10 \pm \sqrt{100 - 96}}{2} \]
\[ = \frac{-10 \pm \sqrt{4}}{2} \]
\[ = \frac{-10 \pm 2}{2} \]

Thus, the solutions are:
\[ r = \frac{-10 + 2}{2} = -4 \]
\[ r = \frac{-10 - 2}{2} = -6 \]

3. **General Solution**: The general solution of the differential equation is a combination of the solutions derived from the characteristic equation, which are \( e^{-4t} \) and \( e^{-6t} \).

Hence, the general solution is:
\[ y(t) = C_1 e^{-4t} + C_2 e^{-6t} \]

Where \( C_1 \) and \( C_2 \) are arbitrary constants determined by initial conditions.

### Summary

We've solved the differential equation \( y'' + 10y' + 24y = 0 \) by:

1. Forming the characteristic equation.
2. Solving the characteristic equation for \( r \).
3. Constructing the general solution using the roots of the characteristic equation.

Understanding this process can help in solving similar second-order linear homogeneous differential equations efficiently.
Transcribed Image Text:### Solving Second-Order Linear Homogeneous Differential Equations In this module, we'll work through solving a second-order linear homogeneous differential equation. Consider the equation given below: \[ y'' + 10y' + 24y = 0 \] To solve this, we'll follow these steps: 1. **Characteristic Equation**: The first step is to form the characteristic (or auxiliary) equation by replacing \( y \) with \( e^{rt} \). This gives: \[ r^2 + 10r + 24 = 0 \] 2. **Solve the Characteristic Equation**: Solve for \( r \) using the quadratic formula \( r = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \). Here, \( a = 1 \), \( b = 10 \), and \( c = 24 \). \[ r = \frac{-10 \pm \sqrt{(10)^2 - 4(1)(24)}}{2(1)} \] \[ = \frac{-10 \pm \sqrt{100 - 96}}{2} \] \[ = \frac{-10 \pm \sqrt{4}}{2} \] \[ = \frac{-10 \pm 2}{2} \] Thus, the solutions are: \[ r = \frac{-10 + 2}{2} = -4 \] \[ r = \frac{-10 - 2}{2} = -6 \] 3. **General Solution**: The general solution of the differential equation is a combination of the solutions derived from the characteristic equation, which are \( e^{-4t} \) and \( e^{-6t} \). Hence, the general solution is: \[ y(t) = C_1 e^{-4t} + C_2 e^{-6t} \] Where \( C_1 \) and \( C_2 \) are arbitrary constants determined by initial conditions. ### Summary We've solved the differential equation \( y'' + 10y' + 24y = 0 \) by: 1. Forming the characteristic equation. 2. Solving the characteristic equation for \( r \). 3. Constructing the general solution using the roots of the characteristic equation. Understanding this process can help in solving similar second-order linear homogeneous differential equations efficiently.
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