### Session Overview

This session begins our study of systems of differential equations. Systems of DE’s have more than one unknown variable. This can happen if you have two or more variables that interact with each other and each influences the other’s growth rate. The first thing we’ll do is to solve a system of linear DE’s using elimination. We do this first, because this method is already available to us right now. Starting in the next session we will learn about matrix methods and these will be our preferred approach to solving and understanding systems of DE’s. |

### Session Activities

Read the course notes:

Watch the lecture video clip:

Read the course notes:

Complete the practice problem:

Watch the lecture video clip:

Read the course notes:

Complete the practice problem:

Read the course notes:

Complete the practice problem:

Learn from the Mathlet materials:

- Read about how to work with the Linear Phase Portraits: Matrix Entry Applet (PDF)
- Work with the Linear Phase Portraits: Matrix Entry Applet

Read the course notes:

Learn from the Mathlet materials:

- Read about how to work with the
*Companion Matrix*option in the Linear Phase Portraits: Matrix Entry Applet (PDF) - Work with the
*Companion Matrix*option in the Linear Phase Portraits: Matrix Entry Applet

### Check Yourself

Take the quiz:

### Session Activities

Watch the problem solving video:

Complete the practice problems:

### Check Yourself

Complete the problem sets: