English
If a ∣ a and a ≠ 0, then v_p(a/b) = v_p(a) − v_p(b) for b ≠ 0.
Русский
Если b делит a и a ≠ 0, тогда v_p(a/b) = v_p(a) − v_p(b) для b ≠ 0.
LaTeX
$$$ a \\neq 0 \\land b \\mid a \\Rightarrow v_p\\left(\\dfrac{a}{b}\\right) = v_p(a) - v_p(b) $$$
Lean4
/-- A rewrite lemma for `padicValNat p (a * b)` with conditions `a ≠ 0`, `b ≠ 0`. -/
protected theorem mul : a ≠ 0 → b ≠ 0 → padicValNat p (a * b) = padicValNat p a + padicValNat p b :=
mod_cast padicValRat.mul (p := p) (q := a) (r := b)