7t Two solutions to y''+ 11y' + 28y = 0 are yi = e , 42 = e-4t. a) Find the Wronskian. W = b) Find the solution satisfying the initial conditions y(0) = 0, y'(0) = - 18

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Chapter2: Second-order Linear Odes
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**Differential Equations - Problem Solving**

**Problem Statement:** 

Two solutions to the differential equation \( y'' + 11y' + 28y = 0 \) are \( y_1 = e^{-7t} \) and \( y_2 = e^{-4t} \).

a) Find the Wronskian.
\[ W = \_\_\_\_\_\_ \]

b) Find the solution that satisfies the initial conditions \( y(0) = 0 \), \( y'(0) = -18 \).
\[ y = \_\_\_\_\_\_ \]

---

**Solution Approach:**

1. **Wronskian Calculation:**
   The Wronskian \( W \) of two solutions \( y_1(t) \) and \( y_2(t) \) is given by:
   \[ W = y_1(t) y_2'(t) - y_2(t) y_1'(t). \]

   - For \( y_1(t) = e^{-7t} \):
     \[ y_1'(t) = -7e^{-7t}. \]

   - For \( y_2(t) = e^{-4t} \):
     \[ y_2'(t) = -4e^{-4t}. \]

   Substituting into the Wronskian formula:
   \[ W = e^{-7t} (-4e^{-4t}) - e^{-4t} (-7e^{-7t}). \]

2. **Finding the Particular Solution:**
   We can express the general solution of the differential equation as:
   \[ y(t) = C_1 y_1(t) + C_2 y_2(t) = C_1 e^{-7t} + C_2 e^{-4t}. \]

   Using the initial conditions \( y(0) = 0 \) and \( y'(0) = -18 \):

   - At \( t = 0 \):
     \[ y(0) = C_1 e^{0} + C_2 e^{0} = C_1 + C_2 = 0. \]

     Therefore, \( C_1 + C_2 = 0 \).

   - The derivative of \( y \) is:
     \[ y'(t) = -7C
Transcribed Image Text:**Differential Equations - Problem Solving** **Problem Statement:** Two solutions to the differential equation \( y'' + 11y' + 28y = 0 \) are \( y_1 = e^{-7t} \) and \( y_2 = e^{-4t} \). a) Find the Wronskian. \[ W = \_\_\_\_\_\_ \] b) Find the solution that satisfies the initial conditions \( y(0) = 0 \), \( y'(0) = -18 \). \[ y = \_\_\_\_\_\_ \] --- **Solution Approach:** 1. **Wronskian Calculation:** The Wronskian \( W \) of two solutions \( y_1(t) \) and \( y_2(t) \) is given by: \[ W = y_1(t) y_2'(t) - y_2(t) y_1'(t). \] - For \( y_1(t) = e^{-7t} \): \[ y_1'(t) = -7e^{-7t}. \] - For \( y_2(t) = e^{-4t} \): \[ y_2'(t) = -4e^{-4t}. \] Substituting into the Wronskian formula: \[ W = e^{-7t} (-4e^{-4t}) - e^{-4t} (-7e^{-7t}). \] 2. **Finding the Particular Solution:** We can express the general solution of the differential equation as: \[ y(t) = C_1 y_1(t) + C_2 y_2(t) = C_1 e^{-7t} + C_2 e^{-4t}. \] Using the initial conditions \( y(0) = 0 \) and \( y'(0) = -18 \): - At \( t = 0 \): \[ y(0) = C_1 e^{0} + C_2 e^{0} = C_1 + C_2 = 0. \] Therefore, \( C_1 + C_2 = 0 \). - The derivative of \( y \) is: \[ y'(t) = -7C
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