Section 22.5

Solutions to Systems

Just like solves , we will find that solves .

1

Introduction

We guess a solution of the form:

Plugging this into gives , or .
This is why eigenvalues matter!

2

General Solution

Superposition

If is and has linearly independent eigenvectors , the general solution is:

3

Visual: Phase Portrait

Interactive: Flow

The solution curve is a combination of flow along the "Eigen-axes".

4

Worked Examples

Example 1: Solving Diagonal System

Solve .

1. Decoupled:

.

.

2. Vector Form:

.

Eigenvalues are 3, -2. Eigenvectors are standard basis.

Example 2: General Solution

Given eigenvalues and . Write general solution.

1. Assemble:

.

.

.

Example 3: IVP

Use Example 2 with .

1. Plug in t=0:

.

2. Solve System:

.

.

Subtract: . Then .

3. Final Answer:

.

5

Practice Quiz

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