DEFINITIONZ 函数 If f is a function from A to b, we say that a is the domain of f and B is the codomain of f. If f(a)=b, we say that b is the image of a and a is a pre-image of b. The range of f is the set of all images of elements of A. Also, if f is a function from A to B, we say that f maps a to B A:定义域/ domain of f a:b的原象/pre-mage B:陪域/ codomain of f b:a的象/ mage f(A):值域/ range of fF u n c t i o n s 函 数 DEFINITION 2. If f is a function from A to B, we say that A is the domain of f and B is the codomain of f. If f (a) = b , we say that b is the image of a and a is a pre-image of b. The range of f is the set of all images of elements of A. Also, if f is a function from A to B, we say that f maps A to B. A：定义域/domain of f a: b 的原象/pre-image B：陪域/codomain of f b: a的象/image f（A）：值域/range of f