An important word: derivative!

(I'll tell you in the most popular words) The derivative we often use is an apostrophe on Y, and in college it is dy/dx, and dy is differential, so you can take the derivative first, and then move dx to the side, that's all. The essence is to add dx after the derivative! !

Indefinite integral is the inverse operation of derivative, and the solved derivative is known, so you can find the original number!

A definite integral is a solution with a certain range. What the book says is very troublesome and difficult to understand. You can forget those things first, unless you take the postgraduate entrance examination, or you can use my understanding. It is best to recite ready-made formulas. In fact, those can be deduced by themselves. Do you have this feeling, hehe, but for convenience, you have to recite it, hehe, exchange little experiences, hehe.