x = 4
y = -2 is the equation of a horizontal line parallel to the x- axis , passing through all points with a y- coordinate = - 2
A line perpendicular to y = - 2 will be a vertical line parallel to the y- axis with equation x = c where c is the value of the x- coordinate the line passes through.
the line passes through (4 , - 2) with x- coordinate 4
equation of perpendicular line is x = 4