Consider the linear differential equation ay" - xy' + y = 0. (a) Verify that y = x is a solution to this DE. (i.e., show that y1 = I satisfies the DE.) (b) Use the method of reduction of order to find a second lin. indep. solution y2. Hint: For reduction of order, suppose that y2 = uY1.

Advanced Engineering Mathematics
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ISBN:9780470458365
Author:Erwin Kreyszig
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Chapter2: Second-order Linear Odes
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## Example Problem: Solving a Linear Differential Equation

Consider the linear differential equation:
\[ x^3 y'' - xy' + y = 0 \]

### Steps to Solve:

**(a)** Verify that \( y_1 = x \) is a solution to this differential equation (i.e., show that \( y_1 = x \) satisfies the DE).

**(b)** Use the method of reduction of order to find a second linearly independent solution \( y_2 \).

**Hint:** For reduction of order, suppose that \( y_2 = uy_1 \).

---

### Solution Outline:

1. **Verification of \( y_1 = x \) as a Solution:**
   - To verify that \( y_1 = x \) is a solution, substitute \( y_1 = x \) into the differential equation and confirm that the left-hand side equals zero.

2. **Reduction of Order:**
   - Given the first solution \( y_1 = x \), find the second solution by assuming \( y_2 = uy_1 \), where \( u \) is a function of \( x \).
   - Derive the necessary expressions and substitute back into the original differential equation to solve for \( u \).

---

### Detailed Solution Process:

**Verification:**

1. Let \( y_1 = x \)
2. Compute the required derivatives:
   - \( y_1' = 1 \)
   - \( y_1'' = 0 \)
3. Substitute these into the differential equation \( x^3 y'' - xy' + y \):
   \[
   x^3 (0) - x(1) + x = 0
   \]
4. Simplify to show:
   \[
   -x + x = 0
   \]
   This confirms that \( y_1 = x \) satisfies the differential equation.

**Reduction of Order:**

1. Assume \( y_2 = uy_1 = ux \)
2. Compute the derivatives needed for substitution:
   - \( y_2' = u'x + u \)
   - \( y_2'' = u''x + 2u' \)
3. Substitute \( y_2, y_2', y_2'' \) into the differential equation:
   \[ x^3 (u''x + 2u') - x(u'x +
Transcribed Image Text:--- ## Example Problem: Solving a Linear Differential Equation Consider the linear differential equation: \[ x^3 y'' - xy' + y = 0 \] ### Steps to Solve: **(a)** Verify that \( y_1 = x \) is a solution to this differential equation (i.e., show that \( y_1 = x \) satisfies the DE). **(b)** Use the method of reduction of order to find a second linearly independent solution \( y_2 \). **Hint:** For reduction of order, suppose that \( y_2 = uy_1 \). --- ### Solution Outline: 1. **Verification of \( y_1 = x \) as a Solution:** - To verify that \( y_1 = x \) is a solution, substitute \( y_1 = x \) into the differential equation and confirm that the left-hand side equals zero. 2. **Reduction of Order:** - Given the first solution \( y_1 = x \), find the second solution by assuming \( y_2 = uy_1 \), where \( u \) is a function of \( x \). - Derive the necessary expressions and substitute back into the original differential equation to solve for \( u \). --- ### Detailed Solution Process: **Verification:** 1. Let \( y_1 = x \) 2. Compute the required derivatives: - \( y_1' = 1 \) - \( y_1'' = 0 \) 3. Substitute these into the differential equation \( x^3 y'' - xy' + y \): \[ x^3 (0) - x(1) + x = 0 \] 4. Simplify to show: \[ -x + x = 0 \] This confirms that \( y_1 = x \) satisfies the differential equation. **Reduction of Order:** 1. Assume \( y_2 = uy_1 = ux \) 2. Compute the derivatives needed for substitution: - \( y_2' = u'x + u \) - \( y_2'' = u''x + 2u' \) 3. Substitute \( y_2, y_2', y_2'' \) into the differential equation: \[ x^3 (u''x + 2u') - x(u'x +
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