English
If j is a ring hom S → Q such that j(algebraMap_R_S x) = map Q g hy (algebraMap_R_S x) for all x, then j = map Q g hy.
Русский
Если j — кольцевой гомоморфиз S → Q и выполняется j(algebraMap_R_S x) = map Q g hy (algebraMap_R_S x) для всех x, то j = map Q g hy.
LaTeX
$$$ \\text{If } j : S \\to Q, \\ \\forall x,\\ j(\\mathrm{algebraMap}_{R,S} x) = \\mathrm{map}\\;Q\\;g\\;hy\\ (\\mathrm{algebraMap}_{R,S} x) \\Rightarrow \\mathrm{map}\\;Q\\;g\\;hy = j. $$$
Lean4
theorem map_unique (j : S →+* Q) (hj : ∀ x : R, j (algebraMap R S x) = algebraMap P Q (g x)) : map Q g hy = j :=
lift_unique (fun y => map_units _ ⟨g y, hy y.2⟩) hj