You can go to Youku.com, where there are many videos of famous teachers, and I have seen them very well. Search online for a series of compulsory xxx.

You can also go to the college entrance examination resource network or the library to find such materials. There are quite a lot of materials. If you go to math, set, inequality (basic inequality is very important) and power exponential pair function in your freshman year. (Note that the top high school students in the bookstore are really good at math. After reading it, you can do some small topics, and your grades will be excellent. The Longmen series is very difficult. It is best to watch it after you go to school. )