Horizontal line

Definition

A horizontal line is a straight line that runs left to right and has a constant y-value for all points. Its slope is zero because there is no vertical change as you move along the line.

5 Must Know Facts For Your Next Test

1. A horizontal line has the equation of the form $y = c$, where $c$ is a constant.
2. The slope of a horizontal line is 0.
3. A horizontal line intersects the y-axis at point $(0, c)$.
4. In the Cartesian plane, horizontal lines are parallel to the x-axis.
5. Horizontal lines can be used to test whether a function is one-to-one using the Horizontal Line Test.

Review Questions

• What is the general equation for a horizontal line?
• What is the slope of a horizontal line?
• If a horizontal line passes through (4, -2), what is its equation?

Related terms

Slope:

The measure of steepness or incline of a line, calculated as rise over run.

Vertical Line: A straight line that runs up and down with an undefined slope and an equation of the form $x = k$.

Slope-Intercept Form:

$y = mx + b$, where $m$ represents the slope and $b$ represents the y-intercept.