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}