Question

What is a vertical line with a rise over run relationship that does not exist.

Answer 1

I think the best way to explain this is that the rise over run of the vertical line is consider as 1/0 which means that the said equation has a y coordinate of zero and any number that has a denominator of zero is undefined, so the slope of the vertical line is undefined. I hope this would help 

Answer 2

If the line is vertical, it means that the slope is undefined: it has no value that we can calculate. Hope that helps you.