1.NounFor a given function, the set of all elements of the domain that are mapped into a given subset of the codomain; given a function ƒ : X → Y and a subset B ⊆ Y, the set ƒ(B) = {x ∈ X : ƒ(x) ∈ B}."The preimage of
{
4
,
9
}
{\displaystyle \{4,9\}}
under the function
f
:
R
→
R
:
f
(
x
)
=
x
2
{\displaystyle f:\mathbb {R} \rightarrow \mathbb {R} :f(x)=x^{2}}
is the set
{
−
3
,
−
2
,
+
2
,
+
3
}
{\displaystyle \{-3,-2,+2,+3\}}
."