English
Subtraction preserves cast: (cast (a - b : ZMod n) : R) = cast a - cast b.
Русский
Вычитание сохраняет приведение: cast(a-b) = cast a - cast b.
LaTeX
$$$\\\\forall {n : \\\\mathbb{N}} {R : Type*} [Ring R] [CharP R n] (a b : ZMod n), \\\\operatorname{cast} (a - b) = \\\\operatorname{cast} a - \\\\operatorname{cast} b$$$
Lean4
theorem cast_sub' (a b : ZMod n) : (cast (a - b : ZMod n) : R) = cast a - cast b := by simp