You can
put this solution on YOUR website!(-6.2,18.1) and (-3.4,18.1).
slope=(18.1-18.1)/-3.4+6.2
slope=0/(-3.4+6,2)
slope = 0 or this is a verticle line through y=18.1
the line formula is:
y=18.1

(graph 300x200 pixels, x from -6 to 5, y from -10 to 20, y = 18.1).