Strictly speaking, someone once solved the derivative problem in the college entrance examination and used the symbol of the second derivative, which belongs to the university category. The teacher told us that when we looked up many math books, as long as there was a symbol of the second derivative written in it, we would give points, and finally found none, so that person didn't get full marks for this question.

However, if the first two stages use knowledge that has not been learned in junior high school, it is ok to use knowledge that has not been learned in senior high school in the first two stages.