多元函数 定义 11.2.1 设 D 是 n R 上的点集,D 到 R 的映射 f : D →R, x 6 z 称为 n 元函数,记为 = fz x)( 。这时,D 称为 f 的定义域, f D)( = ∈ R = fzz xx ∈ D}),(|{ 称为 f 的值域,Γ= }),(|),{( 1 R ∈=∈ D + x fzz xx n 称 为 f 的图象
Let A and B be sets. A function f from A to B is an assignment of exactly one element of B to each element of A. We write f(a) = b if b is the unique element of B assigned by the function f to the element a of A. If f is a function from A to B, we write f : A→B