Metamath Proof Explorer

Theorem difeq2i

Description: Inference adding difference to the left in a class equality. (Contributed by NM, 15-Nov-2002)

Ref Expression
Hypothesis difeq1i.1 A = B
Assertion difeq2i C A = C B


Step Hyp Ref Expression
1 difeq1i.1 A = B
2 difeq2 A = B C A = C B
3 1 2 ax-mp C A = C B