We often encounter such a situation, after solving a certain step, we can't continue with a unified method and formula. This is because the research object contains a variety of situations, which requires classifying all situations, solving them one by one, and then summarizing them to get a solution. This is a confidential discussion. There are many reasons for classified discussion. There are many situations in the mathematical concept itself, such as the limitation of mathematical operation rules, some theorems and formulas, the uncertainty and change of graphic position, etc. When discussing and solving problems by classification, we should unify the standards, and we should not focus on them or leave them out.