Then, as you said, every point may have a limit, but even if there is a limit, every point can only have one limit.
The positive infinity and negative infinity of a function are two limits, the positive infinity limit is unique and the negative infinity limit is unique, which is the uniqueness of the function limit.
Ways to learn mathematics well:
1. Mathematics, like other disciplines, has many conceptual things. The basis of learning mathematics well is to understand what the definition is about.
For example, the meaning of square, cube and absolute value in mathematics. We know that a square is the product of two identical numbers. Of course, a cube is the product of three identical numbers, and the absolute value is a value greater than or equal to 0. Knowing the true meaning of the definition, we took the first step and laid a solid foundation for the following study.
The difference between mathematics and other subjects is that there is no need to memorize, because mathematics does not test questions, but calculates, which is the biggest difference. How to practice specifically.
Many problems in mathematics are based on definitions. As I said before, once you understand the definition, it's easy to start. For example, if you want to merge similar items, you must first define them, that is, similar items. Simply put, it is something that everyone has. If you understand the definition, you will get twice the result with half the effort.
As I said before. Mathematics is not learned by rote, but worked out with a pen. Therefore, for a formula or a definition, only by doing a few more questions about this problem can we use it naturally and truly understand its meaning.
Therefore, for mathematics, we must not be lazy, just look at it without doing it. Only by using more brains and hands can we learn mathematics more flexibly.