# How do you find the equation of the line perpendicular to the line y=5 and passing through (5, 4)?

Since the graph of $y = 5$ is a horizontal line, any line perpendicular to a horizontal line is a vertical line, whose equation can be written in the form $x = a$. Since it passes through the point $\left(5 , 4\right)$, so the equation is:
$x = 5$