8+ 6+ 4+ 2+ 2 ++ 6 8 -8 -6 -4 2 ܠܛ -4+ -6+ -8+ What is the equation of the line?

The lines whose equation is x = a, are vertical lines that pass through the point (a, y) where y is any real number. Additionally, vertical lines have an indefinite slope.
You can see it in the graph of this equation: