English Dictionary

preimage

noun

(mathematics) For a given function, the set of all elements of the domain that are mapped into a given subset of the codomain; (formally) given a function ƒ : X → Y and a subset B ⊆ Y, the set ƒ⁻¹(B) = {x ∈ X : ƒ(x) ∈ B}.

The preimage of the function f is the set of all elements in the domain that map to a given element in the codomain.

意味（1）

(mathematics) For a given function, the set of all elements of the domain that are mapped into a given subset of the codomain; (formally) given a function ƒ : X → Y and a subset B ⊆ Y, the set ƒ⁻¹(B) = {x ∈ X : ƒ(x) ∈ B}.

The preimage of 4,9 under the function f: R → R :f(x)=x² is the set -3,-2,+2,+3.