how do I find an equation perpendicular to x=4 passing threw points (9,9)

Question

I am lost on how to find the perpendicular line to x=4 passing threw points(9,9). Please help

Answer 1

The line x=4 is a vertical line though the point x=4.  A line perpendicular to it will be a horizontal line of the form y = a constant.  Since the line they want goes through (not threw) (9,9), the line is y = 9.