simpa [(show e ≠ f by rintro rfl; exact hf he.mem_ground)] using heX
α : Type u_1
inst✝ : DecidableEq α
M M' : Matroid α
e f x : α
I C : Set α
he : M.Nonloop e
hf : f ∉ M.E
X : Set α
heX : ¬(f ∈ (M.parallelExtend e f).cl (X \ {f}) ∧ e ∉ {f})
hfX : f ∉ X
⊢ f ∉ (M.parallelExtend e f).cl (X \ {f})
no goals