Horizontal Line

A horizontal line is a line that is parallel to the x-axis of the coordinate plane.

The general equation of a horizontal line is $y=c$ where $c$ is a constant. In $y=c$ , it implies that the y-value of the horizontal line is the same or never changes. However, the x-value of the horizontal line can take any values.

If you take any two points of a horizontal line and find the slope, it will always equal to zero. That is why all horizontal lines have a slope of zero, $m=0$ .

Example: Graph $y=3$ .

Since the y-value doesn’t change, we can describe at least five points or ordered pairs that lie on the horizontal line, $y=3$ which can be $(-2,3)$ , $(-1,3)$ , $(0,3)$ , $(1,3)$ , and $(2,3)$ . Plotting these points on the coordinate plane reveals a horizontal line.

the graph of horizontal line y=3 on the xy-plane