In math many times you are asked to show the value that a function approaches instead of actually solving for a function at a given point. When you are searching for where a function approaches you are looking for the limit.
You will see this written in the form:
Usually after this they will define what the function, f(x), is so that you can solve the problem. In this instance we are looking for the limit of f(x) as x approaches C from both sides. It's very important to know that you are looking at the limit as it approaches from both sides of C.
Watch the math video below for a detailed explanation!