Identify the slope of the line shown in the graph below:

Graph of a vertical line with an x intercept of 3

I believe the slope of any vertical line is "undefined" because slope = rise (change in y values) / run (change in x values).

Therefore, the slope for a horizontal line is

m = 0 / (x2-x1).

However, for a vertical line the x-values are the values that are not changing. So, m = (y2-y1) / 0. It is not possible to divide anything by zero. So, the slope of a vertical line is reported as m = undefined.

Any questions?