# Differential Equations

### Why are we studying this?

There are many applications of differential equations, including the following (which we meet later in this chapter):

Differential equations are a special type of integration problem.

Here is a simple differential equation of the type that we met earlier in the Integration chapter:

We didn't call it a differential equation before, but it is one. We'll see several different types of differential equations in this chapter.

Before we see how to solve differential equations, let's see an example of them in action in the AIDS example.