① Matching method: it is transformed into a quadratic function and evaluated by using the characteristics of the quadratic function; Often converted into:;

(2) Reverse solution: the value range used to represent, and then the value range obtained by solving the inequality; Commonly used to solve, such as:

(4) Substitution method: transforming variables into functions of assignable fields and returning to ideas;

⑤ Triangular Bounded Method: Transform it into a function containing only sine and cosine, and use the boundedness of trigonometric function to find the domain;

⑥ Basic inequality methods: transformation and modeling, such as: using the average inequality formula to find the domain;

⑦ Monotonicity method: The function is monotonous, and the domain can be evaluated according to the monotonicity of the function.

⑧ Number-shape combination (mirror image method): According to the geometric figure of the function, use the method of number-shape combination to find the domain.