关于函数的定义

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请见本教材第一章第1.2节关于函数的序偶定义：

DEFINITION

A real fimction of one variable is a set f of ordered pairs of real numbers such that for every real number a one of the following two things happens:

(i) There is exactly one real number b for which the ordered pair (a, b) is a member of f. In this case we say that f(a) is defined and we write f(a) = b. The number b is called the value of f at a.

(ii) There is no real number b for which the ordered pair (a, b) is a member of f. In this case we say that f(a) is undefined.

Thus f(a) = b means that the ordered pair (a, b) is an element of f. Here is one way to visualize a function. Imagine a black box labeled f as in Figure 1.2.1. I（在此省略）

说明：此件系定于7月3日上午向教育部高教司理工处汇报工作之用，

袁萌摘抄于2018年7月1日