First let's take a look at the point (-5,-2) in the plane:
since we want an equation of a line that is perpendicular to the x-axis, it should look like this:
Therefore, the equation is x = -5. Now for the slope, we can easily see that the line passes through the points (-5,-2) and (-5,-3), so, if we calculate the slope we get something like this:
which clearly is undefined.