Theorem subnegi

Description: Relationship between subtraction and negative. (Contributed by NM, 1-Dec-2005)

	Ref	Expression
Hypotheses	negidi.1	|- A e. CC
	pncan3i.2	|- B e. CC
Assertion	subnegi	|- ( A - -u B ) = ( A + B )

Proof

Step	Hyp	Ref	Expression
1		negidi.1	|- A e. CC
2		pncan3i.2	|- B e. CC
3		subneg	|- ( ( A e. CC /\ B e. CC ) -> ( A - -u B ) = ( A + B ) )
4	1 2 3	mp2an	|- ( A - -u B ) = ( A + B )