I learned to draw functions in junior high school. Although I don't know what grade you are in, according to your question, at least you are a senior three.

Draw coordinate axes, find special points and connect lines.

How to find characteristics, monotonicity of functions, extremum of functions and coordinates of extremum points. Because high school functions are basic elementary functions, there is no need to consider the continuity of functions. With these, basically any function can be roughly drawn. When analyzing the purpose of the problem, you only need to know what the function image looks like to analyze it.

Take positive infinity as an example. Positive infinity is not a number, its symbol is ∞.

Generally speaking, a function or expression tends to infinity. It can be understood that for any given positive number m (no matter how big it is), there is always a positive number δ, as long as X is suitable for inequality 0.

So is negative infinity. This concept is the most basic and core knowledge of advanced mathematics. Maybe many people don't understand it very well.