rw [h2] at h'
case a.mp
t : ℕ
P : ℕ → ℕ
h : Balanced t P
this : ∀ (i : ℕ), i ∈ range (t + 1) → P i = minP t P ∨ P i = minP t P + 1
a : ℕ
h' : a ∈ range (t + 1) ∧ P a = minP t P + 1
h2 : P a = minP t P
⊢ False
case a.mp
t : ℕ
P : ℕ → ℕ
h : Balanced t P
this : ∀ (i : ℕ), i ∈ range (t + 1) → P i = minP t P ∨ P i = minP t P + 1
a : ℕ
h' : a ∈ range (t + 1) ∧ minP t P = minP t P + 1
h2 : P a = minP t P
⊢ False