The proof method of increment is to take X 1 < X2, if F (X 1) < F (X2) (both less than, equal to the same direction, that is, the same direction relationship, so F (X) is increasing function.
The proof method of decline is to take x 1 < x2. If f(x 1) > (x2) (one is less than and the other is greater than, the inequality is opposite, that is, the inverse relationship, so f(x) is a decreasing function.
Parity is symmetric (odd function is symmetric about the origin, and even functions are symmetric about the Y axis).
Judgment method: first find f (-x), and then compare it with f(x). If f (-x) =-f (x) is odd function and f (-x = f (x) is an even function.
In a word, as long as the definition of concepts is mastered in mathematics, other problems are only comparison and deformation.
Learn by yourself, understand the definitions and formulas, study the examples, then cover the examples and do the examples yourself to see if the answers are basically the same as those of the examples. If it is consistent, it means that you have understood.