Chapter 3 Functions 今3.1 Introduction g Definition3. 1: Let A and b be nonempty sets. A relation is a(everywhere)function from A to B, denoted by f:A→>B, if for every a∈A, there is one and only b eB so that(a, bEf, we say that b-f(a). The set a is called the domain of the function f. If XCA, then f(X)--falaeX is called the image of X. The image of A itself is called the range of f, we write RelfYcB, thenf(Y=af(aEY, is called the preimage of Y A function f: A>B is called a mapping. If(a, b) fso that b=f(a), then we say that the element a is mapped to the element b.Chapter 3 Functions ❖ 3.1 Introduction ❖ Definition3.1: Let A and B be nonempty sets. A relation is a (everywhere)function from A to B, denoted by f : A→B, if for every aA, there is one and only b B so that (a,b) f, we say that b=f (a). The set A is called the domain of the function f. If XA, then f(X)={f(a)|aX} is called the image of X. The image of A itself is called the range of f, we write Rf . If YB, then f -1 (Y)={a|f(a)Y} is called the preimage of Y. A function f : A→B is called a mapping. If (a,b) f so that b= f (a), then we say that the element a is mapped to the element b