English
For PadicInt x, there exists a unique n with n < p and x − n in the maximal ideal.
Русский
Для PadicInt x существует единственное n, с n < p и x − n ∈ максимальный идеал.
LaTeX
$$$\\\\exists! n \\\\in \\\\mathbb{N}, n < p \\\\land x - n \\\\in maximalIdeal(\\\\mathbb{Z}_{p})$$$
Lean4
theorem existsUnique_mem_range : ∃! n : ℕ, n < p ∧ x - n ∈ maximalIdeal ℤ_[p] :=
by
obtain ⟨n, hn₁, hn₂⟩ := exists_mem_range x
use n, ⟨hn₁, hn₂⟩, fun m ⟨hm₁, hm₂⟩ ↦ ?_
have := (zmod_congr_of_sub_mem_max_ideal x n m hn₂ hm₂).symm
rwa [ZMod.natCast_eq_natCast_iff, ModEq, mod_eq_of_lt hn₁, mod_eq_of_lt hm₁] at this