English
In a preadditive category, for f,g: X → Y with w factoring f+g through P, wf through f, wg through g, the factorThrough of the sum equals the sum of the factorThroughs.
Русский
В предадитивной категории факторизация через сумму равна сумме факторизаций: P.factorThru (f+g) w = P.factorThru f wf + P.factorThru g wg.
LaTeX
$$$P.\text{factorThru} (f+g)\; w = P.\text{factorThru} f\; wf + P.\text{factorThru} g\; wg$$$
Lean4
theorem factorThru_add {X Y : C} {P : Subobject Y} (f g : X ⟶ Y) (w : P.Factors (f + g)) (wf : P.Factors f)
(wg : P.Factors g) : P.factorThru (f + g) w = P.factorThru f wf + P.factorThru g wg :=
by
ext
simp