A derivative can be used to describe the rate of change at a single point, or the *instantaneous velocity*.

The formula used to calculate the average rate of change looks like this:
$$ \dfrac{f(b) - f(a)}{b - a} $$
Interpreting it, this can be described as the change in $y$ over the change in $x$.

- Speed is always positive
- Velocity is directional

As the distance between the two points


# Line Types
## Secant Line
A **Secant Line** connects two points on a graph.

A **Tangent Line** represents the rate of change or slope at a single point on the graph.