Example

Write equations for the horizontal and vertical lines through $(-4,7)$.

Solution

Horizontal lines have equations of the form $y=b$. In order to pass through the given point, we must have $b=7$. The horizontal line through $(-4,7)$ is described by

Vertical lines have equations of the form $x=a$. In order to pass through the given point, we must have $a=-4$. The vertical line through $(-4,7)$ is described by