If you're dealing with some type of a function that has all sorts of special cases, and it's piecewise defined, as we've seen in previous other videos, I would be a little bit more skeptical. Or if you know visually around that point there's some type of jump, or some type of discontinuity, you've got to be a little bit more careful. But in general, this is a pretty good rule of thumb. If you're dealing with plain vanilla functions that are continuous, if you evaluate at x equals a, and you get a real number, that's probably going to be the limit. But now let's think about the other scenarios. What happens if you evaluate it, and you get some number divided by zero? Well, that case, you are probably dealing with a vertical asymptote.