English
The kernImage of f with respect to s is the set of y such that every x with f(x) = y belongs to s.
Русский
KernImage f s — множество y such that для всех x с f(x) = y следует x ∈ s.
LaTeX
$$$y \\in \\operatorname{kernImage}(f,s) \\iff \\forall x\\ \\bigl(f(x)=y \\Rightarrow x \\in s\\bigr)$$$
Lean4
/-- `kernImage f s` is the set of `y` such that `f ⁻¹ y ⊆ s`. -/
def kernImage (f : α → β) (s : Set α) : Set β :=
{y | ∀ ⦃x⦄, f x = y → x ∈ s}