Metamath Proof Explorer

Theorem difeq1d

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

Ref Expression
Hypothesis difeq1d.1 φ A = B
Assertion difeq1d φ A C = B C


Step Hyp Ref Expression
1 difeq1d.1 φ A = B
2 difeq1 A = B A C = B C
3 1 2 syl φ A C = B C