simpa [ne_univ_iff_exists_not_mem, mem_singleton_iff] using exists_ne i₀
ι : Type u_1
α : Type u_2
M : Matroid α
B I J X X' Y Y' F : Set α
Xs Ys Js Is : ι → Set α
i j : ι
e f : α
inst✝ : Nontrivial ι
h : M.ModularFamily Xs
i₀ : ι
⊢ {i₀} ≠ univ
no goals