2. Find a differential equation whose general solution is y(t) = c₁e²t + c₂e-t

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Chapter1: Functions And Models
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### Differential Equations Problem

**Problem Statement:**
Find a differential equation whose general solution is \( y(t) = c_1 e^{2t} + c_2 e^{-t} \).

**Explanation:**
The problem asks you to determine a differential equation for which the given function \( y(t) = c_1 e^{2t} + c_2 e^{-t} \) is a general solution. This type of problem is common in the study of differential equations, where you work backward from a known solution to find the corresponding differential equation.

**Approach:**
1. **Identify the form of the given solution:**
   The given function \( y(t) = c_1 e^{2t} + c_2 e^{-t} \) suggests that the solution is a linear combination of exponential functions.

2. **Determine the characteristic equation:**
   For a homogeneous linear differential equation with constant coefficients, the general solution can often be expressed as a combination of exponential functions. Assume a solution of the form \( y(t) = e^{rt} \). Substitute this into a general second-order linear differential equation \( ay'' + by' + cy = 0 \).

   The characteristic equation associated with the given solution can be determined by finding the roots which in this case are \( r = 2 \) and \( r = -1 \). Therefore, the characteristic equation is:
   \[
   (r - 2)(r + 1) = 0 \Rightarrow r^2 - r - 2 = 0
   \]

3. **Form the differential equation:**
   Given the characteristic equation \( r^2 - r - 2 = 0 \), the corresponding differential equation is:
   \[
   y'' - y' - 2y = 0
   \]

Therefore, the differential equation whose general solution is \( y(t) = c_1 e^{2t} + c_2 e^{-t} \) is:
\[
y'' - y' - 2y = 0
\]

This process demonstrates how to derive the differential equation starting from a given general solution.
Transcribed Image Text:### Differential Equations Problem **Problem Statement:** Find a differential equation whose general solution is \( y(t) = c_1 e^{2t} + c_2 e^{-t} \). **Explanation:** The problem asks you to determine a differential equation for which the given function \( y(t) = c_1 e^{2t} + c_2 e^{-t} \) is a general solution. This type of problem is common in the study of differential equations, where you work backward from a known solution to find the corresponding differential equation. **Approach:** 1. **Identify the form of the given solution:** The given function \( y(t) = c_1 e^{2t} + c_2 e^{-t} \) suggests that the solution is a linear combination of exponential functions. 2. **Determine the characteristic equation:** For a homogeneous linear differential equation with constant coefficients, the general solution can often be expressed as a combination of exponential functions. Assume a solution of the form \( y(t) = e^{rt} \). Substitute this into a general second-order linear differential equation \( ay'' + by' + cy = 0 \). The characteristic equation associated with the given solution can be determined by finding the roots which in this case are \( r = 2 \) and \( r = -1 \). Therefore, the characteristic equation is: \[ (r - 2)(r + 1) = 0 \Rightarrow r^2 - r - 2 = 0 \] 3. **Form the differential equation:** Given the characteristic equation \( r^2 - r - 2 = 0 \), the corresponding differential equation is: \[ y'' - y' - 2y = 0 \] Therefore, the differential equation whose general solution is \( y(t) = c_1 e^{2t} + c_2 e^{-t} \) is: \[ y'' - y' - 2y = 0 \] This process demonstrates how to derive the differential equation starting from a given general solution.
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