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Metamath Proof Explorer

Theorem negeqi

Description: Equality inference for negatives. (Contributed by NM, 14-Feb-1995)

Ref Expression
Hypothesis negeqi.1 ⊢ A = B
Assertion negeqi ⊢ − A = − B

Proof

Step Hyp Ref Expression
1 negeqi.1 ⊢ A = B
2 negeq ⊢ A = B → − A = − B
3 1 2 ax-mp ⊢ − A = − B