Theorem neg1z

Description: -1 is an integer. (Contributed by David A. Wheeler, 5-Dec-2018)

	Ref	Expression
Assertion	neg1z	⊢ - 1 ∈ ℤ

Proof

Step	Hyp	Ref	Expression
1		1nn	⊢ 1 ∈ ℕ
2		nnnegz	⊢ ( 1 ∈ ℕ → - 1 ∈ ℤ )
3	1 2	ax-mp	⊢ - 1 ∈ ℤ