English
For each i, the root i lies in the span over the integers of P.root applied to b.support.
Русский
Для каждого i в P.root i лежит в целочисленном линейном оболочке P.root '' b.support.
LaTeX
$$$P.root_i \\in \\operatorname{span}_{\\mathbb{Z}}(P.root '' b.support).$$$
Lean4
theorem root_mem_span_int (i : ι) : P.root i ∈ span ℤ (P.root '' b.support) :=
by
have := b.root_mem_or_neg_mem i
simp only [← span_nat_eq_addSubmonoidClosure, mem_toAddSubmonoid] at this
rw [← span_span_of_tower (R := ℕ)]
rcases this with hi | hi
· exact subset_span hi
· rw [← neg_mem_iff]
exact subset_span hi