Solve the given differential equation by undetermined coefficients. у" — бу' + 9у %3D 21x + 5 =

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### Solving Differential Equations by Undetermined Coefficients

In this example, we aim to solve the given differential equation using the method of undetermined coefficients.

The differential equation to solve is:

\[ y'' - 6y' + 9y = 21x + 5 \]

The proposed solution \( y(x) \) is:

\[ y(x) = c_1 e^{3x} + c_2 xe^{3x} - \frac{19}{6} x^2 - \frac{17}{9} x \]

Where \( c_1 \) and \( c_2 \) are constants determined by the initial conditions.

#### Explanation of Terms

- **\(e^{3x}\)**: This represents an exponential function with a base \(e\).
- **\(xe^{3x}\)**: This is the exponential function multiplied by \(x\).
- **Constants \(\frac{19}{6}\) and \(\frac{17}{9}\)**: These are coefficients for the polynomial terms \(x^2\) and \(x\), respectively.

#### Understanding the Solution Components

1. **Homogeneous Solution**: 
   The terms \( c_1 e^{3x} \) and \( c_2 xe^{3x} \) constitute the complementary solution derived from solving the homogeneous equation \( y'' - 6y' + 9y = 0 \).

2. **Particular Solution**:
   The polynomial terms \( -\frac{19}{6} x^2 - \frac{17}{9} x \) form the particular solution that specifically satisfies the non-homogeneous part, \( 21x + 5 \).

### Conclusion

By substituting this general solution into the differential equation, we can confirm that it satisfies the given equation. The constants \( c_1 \) and \( c_2 \) will be determined based on initial conditions or additional criteria provided in specific problems.

This elegant blend of exponential functions and polynomials demonstrates the robust capacity of the method of undetermined coefficients to solve a broad range of differential equations.
Transcribed Image Text:### Solving Differential Equations by Undetermined Coefficients In this example, we aim to solve the given differential equation using the method of undetermined coefficients. The differential equation to solve is: \[ y'' - 6y' + 9y = 21x + 5 \] The proposed solution \( y(x) \) is: \[ y(x) = c_1 e^{3x} + c_2 xe^{3x} - \frac{19}{6} x^2 - \frac{17}{9} x \] Where \( c_1 \) and \( c_2 \) are constants determined by the initial conditions. #### Explanation of Terms - **\(e^{3x}\)**: This represents an exponential function with a base \(e\). - **\(xe^{3x}\)**: This is the exponential function multiplied by \(x\). - **Constants \(\frac{19}{6}\) and \(\frac{17}{9}\)**: These are coefficients for the polynomial terms \(x^2\) and \(x\), respectively. #### Understanding the Solution Components 1. **Homogeneous Solution**: The terms \( c_1 e^{3x} \) and \( c_2 xe^{3x} \) constitute the complementary solution derived from solving the homogeneous equation \( y'' - 6y' + 9y = 0 \). 2. **Particular Solution**: The polynomial terms \( -\frac{19}{6} x^2 - \frac{17}{9} x \) form the particular solution that specifically satisfies the non-homogeneous part, \( 21x + 5 \). ### Conclusion By substituting this general solution into the differential equation, we can confirm that it satisfies the given equation. The constants \( c_1 \) and \( c_2 \) will be determined based on initial conditions or additional criteria provided in specific problems. This elegant blend of exponential functions and polynomials demonstrates the robust capacity of the method of undetermined coefficients to solve a broad range of differential equations.
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