One-Sided Limits; Limits at Infinity (Part 1)
Calculus 1 Lecture 1.2 - The concepts of one-sided and infinite limits are touched upon in this introductory video.
Limits only exist when their right-handed and left-handed limits tend toward the same value (or infinity).
When functions cannot be algebraically manipulated to settle on a certain finite limit, try taking the limit from both the left and right sides. You may realize that the limit does not exist.