If you can't learn, why? The main reason is that many definitions of high school are limited to high school, which is not feasible in college mathematics. Learning them will only make you more confused and confused. Yes, in college mathematics, many definitions of high school can't be said to be wrong, but saying that a definition value is limited to high school will not help your high school. If you insist on studying, you must pay attention to distinguish between the definition of high school and the definition of university.