| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							dvmptadd.s | 
							 |-  ( ph -> S e. { RR , CC } ) | 
						
						
							| 2 | 
							
								
							 | 
							dvmptadd.a | 
							 |-  ( ( ph /\ x e. X ) -> A e. CC )  | 
						
						
							| 3 | 
							
								
							 | 
							dvmptadd.b | 
							 |-  ( ( ph /\ x e. X ) -> B e. V )  | 
						
						
							| 4 | 
							
								
							 | 
							dvmptadd.da | 
							 |-  ( ph -> ( S _D ( x e. X |-> A ) ) = ( x e. X |-> B ) )  | 
						
						
							| 5 | 
							
								
							 | 
							dvmptsub.c | 
							 |-  ( ( ph /\ x e. X ) -> C e. CC )  | 
						
						
							| 6 | 
							
								
							 | 
							dvmptsub.d | 
							 |-  ( ( ph /\ x e. X ) -> D e. W )  | 
						
						
							| 7 | 
							
								
							 | 
							dvmptsub.dc | 
							 |-  ( ph -> ( S _D ( x e. X |-> C ) ) = ( x e. X |-> D ) )  | 
						
						
							| 8 | 
							
								5
							 | 
							negcld | 
							 |-  ( ( ph /\ x e. X ) -> -u C e. CC )  | 
						
						
							| 9 | 
							
								
							 | 
							negex | 
							 |-  -u D e. _V  | 
						
						
							| 10 | 
							
								9
							 | 
							a1i | 
							 |-  ( ( ph /\ x e. X ) -> -u D e. _V )  | 
						
						
							| 11 | 
							
								1 5 6 7
							 | 
							dvmptneg | 
							 |-  ( ph -> ( S _D ( x e. X |-> -u C ) ) = ( x e. X |-> -u D ) )  | 
						
						
							| 12 | 
							
								1 2 3 4 8 10 11
							 | 
							dvmptadd | 
							 |-  ( ph -> ( S _D ( x e. X |-> ( A + -u C ) ) ) = ( x e. X |-> ( B + -u D ) ) )  | 
						
						
							| 13 | 
							
								2 5
							 | 
							negsubd | 
							 |-  ( ( ph /\ x e. X ) -> ( A + -u C ) = ( A - C ) )  | 
						
						
							| 14 | 
							
								13
							 | 
							mpteq2dva | 
							 |-  ( ph -> ( x e. X |-> ( A + -u C ) ) = ( x e. X |-> ( A - C ) ) )  | 
						
						
							| 15 | 
							
								14
							 | 
							oveq2d | 
							 |-  ( ph -> ( S _D ( x e. X |-> ( A + -u C ) ) ) = ( S _D ( x e. X |-> ( A - C ) ) ) )  | 
						
						
							| 16 | 
							
								1 2 3 4
							 | 
							dvmptcl | 
							 |-  ( ( ph /\ x e. X ) -> B e. CC )  | 
						
						
							| 17 | 
							
								1 5 6 7
							 | 
							dvmptcl | 
							 |-  ( ( ph /\ x e. X ) -> D e. CC )  | 
						
						
							| 18 | 
							
								16 17
							 | 
							negsubd | 
							 |-  ( ( ph /\ x e. X ) -> ( B + -u D ) = ( B - D ) )  | 
						
						
							| 19 | 
							
								18
							 | 
							mpteq2dva | 
							 |-  ( ph -> ( x e. X |-> ( B + -u D ) ) = ( x e. X |-> ( B - D ) ) )  | 
						
						
							| 20 | 
							
								12 15 19
							 | 
							3eqtr3d | 
							 |-  ( ph -> ( S _D ( x e. X |-> ( A - C ) ) ) = ( x e. X |-> ( B - D ) ) )  |