1. T : Type
2. L1 : T List
3. L2 : T List
4. x : T
5. L1 ≤ L2
6. L1 = (L2 @ [x]) ∈ (T List)
⊢ False
{ (HypSubst' (-1) (-2) THENA Auto) }
5. L2 @ [x] ≤ L2