1, sequence and mathematical induction: sequence is one of the most basic and important concepts in high school mathematics knowledge, involving summation formula, limit, geometric series and so on. The most difficult thing is the derivation of the limit of sequence and the general term formula.

2. Solid geometry: When you first come into contact with solid geometry, you will be confused about the spatial portraits in solid geometry, which will lead to some low-level mistakes in the process of solving problems.