A horizontal line has a rate of change of zero and is considered a constant function. Examples include y=5 and f(x)=-17. A vertical line is not a function because it has the same x-value associated with multiple y-values, so it violates the vertical line test.

1. Horizontal Lines What can you say about the rate of change of a horizontal line? It is zero It is neither increasing or decreasing Therefore it is called a constant function A couple examples are y = 5 f(x) = -17 What is f(4)? What is f(-10012)?

2. Vertical Lines Is the graph of a vertical line a function? Why or why not? It is a set of ordered pairs that satisfy a particular condition For example x = 4 x = -11 Notice they will always have the same x-value associated with multiple y-values so NOT A FUNCTION