Slope-intercept equation

Question

The graph of f passes through (-9,-4) and is perpendicular to the line who's equation is x=15.

Im not understanding how to get the slope-intercept equation of the function

Answer 1

y=-4 is perpendicular to x=15 and goes through the point (-9,-4)

or if you want an explicit slope intercept form

y =(0)x -4 where 0 is the slope and -4 is the y intercept, but (0)x = 0 and drops out to leave y=-4

x=15 is a vertical line. Perpendicular lines to a vertical line have zero slope. zero slope means a flat horizontal line