First of all, if you are rushing to get more than 90% or even full marks on the paper, you will only be exposed to mathematics in Grade One. And if you don't even have a solid grasp of junior high school content, it is meaningless.
If the first condition is satisfied, then the mathematics you need to contact is actually concentrated in one place: linear equations. The flexible application of linear equation can quickly solve some problems of function finale, such as directly multiplying-1 by vertical slope, such as the distance formula from point to straight line, etc. , has high limitations. As for the rest of the content, it is almost useless if it is simply for the senior high school entrance examination.
In fact, if you have this level, or if your school and class are at a high level, generally speaking, the math teacher will tell you these contents, and you don't need to spend any time on self-study. In addition, teachers in extra-curricular remedial classes will also teach you useful parts.
Therefore, if it is only for the senior high school entrance examination, there is no need to spend extra time studying senior high school mathematics. Of course, if it is not utilitarian, but just for interest, then you are welcome.