Metamath Proof Explorer


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