English
For finitely supported f,g : ι →₀ G, the support of f - g is contained in the union of supports: supp(f - g) ⊆ supp(f) ∪ supp(g).
Русский
Для функций с конечной опорой f,g: supp(f - g) ⊆ supp(f) ∪ supp(g).
LaTeX
$$$\operatorname{support}(f - g) \subseteq \operatorname{support}(f) \cup \operatorname{support}(g).$$$
Lean4
theorem support_sub [DecidableEq ι] {f g : ι →₀ G} : support (f - g) ⊆ support f ∪ support g :=
by
rw [sub_eq_add_neg, ← support_neg g]
exact support_add