DEFINITION 1 函数 Let f be a function from the set a to the set B. The graph of the function f is the set of ordered pairs((a, b)|a∈ Aand f(a)=b}
F u n c t i o n s 函 数 DEFINITION 11. Let f be a function from the set A to the set B. The graph of the function f is the set of ordered pairs {(a, b)∣a∈A and f (a) = b}
EXAMPLE 20 函数 Display the graph of the function f(x)=xfrom the set of integers to the set of integers
F u n c t i o n s 函 数 EXAMPLE 20 Display the graph of the function f(x) = x2 from the set of integers to the set of integers
DEFINITION 1 函数 函数的分类
F u n c t i o n s 函 数 DEFINITION 1. 函数的分类
DEFINITIONS 函数 A function f is said to be one-to-one, or injective, if and only f(x)=f(y) implies that x=y for all x and y in the domain of. A function is said to be an injection if it is one-to-one 对一,单函数,单射
F u n c t i o n s 函 数 DEFINITION 5. A function f is said to be one-to-one, or injective, if and only f (x) = f (y) implies that x = y for all x and y in the domain of f. A function is said to be an injection if it is one-to-one. 一对一，单函数，单射
EKAMPLE G 函数 Determine whether the function f from a, b, c, d to(1, 2, 3, 4, 5) with f(a)=4,f(b)=5,f(Cc)=1,andf(d)=3 is one-to-one
F u n c t i o n s 函 数 EXAMPLE 6 Determine whether the function f from {a, b, c, d} to (1, 2, 3, 4, 5) with f(a) = 4, f(b) = 5, f(c) = 1, and f(d) = 3 is one-to-one