Set, as the first math lesson after entering senior high school, has brought challenges to students' learning because of its abstract concept and numerous symbols and terms. However, the idea and method of set runs through high school mathematics and is a very important basic content in the whole high school mathematics. The following are some commonly used methods and skills to solve the set problem. I hope it will be helpful for the students to conquer the fortress set. 1. Element analysis Because the elements in the set are deterministic, mutually different and disorderly, we can analyze the elements from three aspects: element characteristics, set operation and special set, and find a breakthrough to solve the problem. 1. Use the example of element characteristic analysis 1, set m = {y | y = x2-66. Let N={x|y=3-x2, x∈R}, then m ∩ n = () A. {(-2, 1), (2,1)} B. {t | 0 ≤ t ≤ 3. The element in the set n is x, which represents the range of x in the function y=3-x2, so that N={x|-3≤x≤3} represents all real numbers between -3 and 3. It is easy to get m ∩ n = {t |-65438+. ......