Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

The graph of $x=−4$ is a vertical line because all the points on the graph of this equation have an x-coordinate of $−4$. If you plot some points whose x-coordinate is $−4$ then connect the points using a line, you will form a vertical line.
The graph of the equation $x=−4$ is a vertical line because all the points on this line have an x-coordinate of $−4$. This means that the points $(−4, 8)$, $(−4, 0)$, and $(−4, 8)$ are on the line. If you plot and connect these points, you will form a vertical line.