As you probably know, the equation of a line is usually of the form y = mx + b, where m is the slope.

The exception to that is a vertical line. You can't say "y =" anything because there are an infinite number of y values (because the line goes straight up and down). Another way of saying that would be that the slope, m, is infinite.

Therefore, the equation of a vertical line is written instead as x = c, where c is a constant equal to the x-coordinate of the points on the line. Note that there's no y in the equation at all. It's just like the equation of a horizontal line (of the form y = c, where c is a constant), where there's no x in the equation.

So given that, can you figure out what the equation is?