The concept of function is the basis of calculus and the focus of this chapter. To understand the concept of function, we should grasp the following aspects:

(1) correspondence rule and domain are two elements in function definition.

Therefore, two functions are the same only when their corresponding laws and domains are the same.

(2) There are two cases about the definition domain of the function given by the analytic expression: when the actual meaning of the function is not considered, the definition domain of the agreed function is a number set composed of all real numbers that make the analytic expression of the function meaningful; In practical problems, it needs to be determined according to the actual meaning of the problem.

(3) Signs f and f(x) are essentially different.

References:

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