no goals
α : Type u
β : Type ?u.255021
n : ℕ
x : α
inst✝ : LinearOrderedRing α
hn : n ≠ 0
⊢ ∑ i in range n, x ^ i < 0 ↔ Even n ∧ x + 1 < 0
rw [← not_iff_not, not_lt, le_iff_lt_or_eq, eq_comm,
  or_congr (geom_sum_pos_iff hn) (geom_sum_eq_zero_iff_neg_one hn), Nat.odd_iff_not_even, ←
  add_eq_zero_iff_eq_neg, not_and, not_lt, le_iff_lt_or_eq, eq_comm, ← imp_iff_not_or, or_comm,
  and_comm, Decidable.and_or_imp, or_comm]