apply phi_ih
case neg.h
v u x : VarName
phi : Formula
phi_ih : ∀ (binders : Finset VarName), v ∉ binders → admitsAux v u binders phi → fastAdmitsAux v u binders phi
binders : Finset VarName
h1 : v ∉ binders
h2 : admitsAux v u (binders ∪ {x}) phi
c1 : ¬v = x
⊢ fastAdmitsAux v u (binders ∪ {x}) phi
case neg.h.h1
v u x : VarName
phi : Formula
phi_ih : ∀ (binders : Finset VarName), v ∉ binders → admitsAux v u binders phi → fastAdmitsAux v u binders phi
binders : Finset VarName
h1 : v ∉ binders
h2 : admitsAux v u (binders ∪ {x}) phi
c1 : ¬v = x
⊢ v ∉ binders ∪ {x}

case neg.h.h2
v u x : VarName
phi : Formula
phi_ih : ∀ (binders : Finset VarName), v ∉ binders → admitsAux v u binders phi → fastAdmitsAux v u binders phi
binders : Finset VarName
h1 : v ∉ binders
h2 : admitsAux v u (binders ∪ {x}) phi
c1 : ¬v = x
⊢ admitsAux v u (binders ∪ {x}) phi