## Precalculus (6th Edition)

$y$
RECALL: A horizontal line has an equation in the form $y=k$ where $k$ is a real number. All points on the line have a y-coordinate of $k$. The given horizontal line contains the point $(-4, 8)$. The y-coordinate of this point is $8$. Thus, the equation of the horizontal line is $y=8$. Therefore, the missing expression in the given statement is: $y$