| Step | Hyp | Ref | Expression | 
						
							| 1 |  | hodseq.2 |  |-  S : ~H --> ~H | 
						
							| 2 |  | hodseq.3 |  |-  T : ~H --> ~H | 
						
							| 3 |  | neg1cn |  |-  -u 1 e. CC | 
						
							| 4 |  | homulcl |  |-  ( ( -u 1 e. CC /\ T : ~H --> ~H ) -> ( -u 1 .op T ) : ~H --> ~H ) | 
						
							| 5 | 3 2 4 | mp2an |  |-  ( -u 1 .op T ) : ~H --> ~H | 
						
							| 6 |  | hosval |  |-  ( ( S : ~H --> ~H /\ ( -u 1 .op T ) : ~H --> ~H /\ x e. ~H ) -> ( ( S +op ( -u 1 .op T ) ) ` x ) = ( ( S ` x ) +h ( ( -u 1 .op T ) ` x ) ) ) | 
						
							| 7 | 1 5 6 | mp3an12 |  |-  ( x e. ~H -> ( ( S +op ( -u 1 .op T ) ) ` x ) = ( ( S ` x ) +h ( ( -u 1 .op T ) ` x ) ) ) | 
						
							| 8 | 1 | ffvelcdmi |  |-  ( x e. ~H -> ( S ` x ) e. ~H ) | 
						
							| 9 | 2 | ffvelcdmi |  |-  ( x e. ~H -> ( T ` x ) e. ~H ) | 
						
							| 10 |  | hvsubval |  |-  ( ( ( S ` x ) e. ~H /\ ( T ` x ) e. ~H ) -> ( ( S ` x ) -h ( T ` x ) ) = ( ( S ` x ) +h ( -u 1 .h ( T ` x ) ) ) ) | 
						
							| 11 | 8 9 10 | syl2anc |  |-  ( x e. ~H -> ( ( S ` x ) -h ( T ` x ) ) = ( ( S ` x ) +h ( -u 1 .h ( T ` x ) ) ) ) | 
						
							| 12 |  | homval |  |-  ( ( -u 1 e. CC /\ T : ~H --> ~H /\ x e. ~H ) -> ( ( -u 1 .op T ) ` x ) = ( -u 1 .h ( T ` x ) ) ) | 
						
							| 13 | 3 2 12 | mp3an12 |  |-  ( x e. ~H -> ( ( -u 1 .op T ) ` x ) = ( -u 1 .h ( T ` x ) ) ) | 
						
							| 14 | 13 | oveq2d |  |-  ( x e. ~H -> ( ( S ` x ) +h ( ( -u 1 .op T ) ` x ) ) = ( ( S ` x ) +h ( -u 1 .h ( T ` x ) ) ) ) | 
						
							| 15 | 11 14 | eqtr4d |  |-  ( x e. ~H -> ( ( S ` x ) -h ( T ` x ) ) = ( ( S ` x ) +h ( ( -u 1 .op T ) ` x ) ) ) | 
						
							| 16 | 7 15 | eqtr4d |  |-  ( x e. ~H -> ( ( S +op ( -u 1 .op T ) ) ` x ) = ( ( S ` x ) -h ( T ` x ) ) ) | 
						
							| 17 |  | hodval |  |-  ( ( S : ~H --> ~H /\ T : ~H --> ~H /\ x e. ~H ) -> ( ( S -op T ) ` x ) = ( ( S ` x ) -h ( T ` x ) ) ) | 
						
							| 18 | 1 2 17 | mp3an12 |  |-  ( x e. ~H -> ( ( S -op T ) ` x ) = ( ( S ` x ) -h ( T ` x ) ) ) | 
						
							| 19 | 16 18 | eqtr4d |  |-  ( x e. ~H -> ( ( S +op ( -u 1 .op T ) ) ` x ) = ( ( S -op T ) ` x ) ) | 
						
							| 20 | 19 | rgen |  |-  A. x e. ~H ( ( S +op ( -u 1 .op T ) ) ` x ) = ( ( S -op T ) ` x ) | 
						
							| 21 | 1 5 | hoaddcli |  |-  ( S +op ( -u 1 .op T ) ) : ~H --> ~H | 
						
							| 22 | 1 2 | hosubcli |  |-  ( S -op T ) : ~H --> ~H | 
						
							| 23 | 21 22 | hoeqi |  |-  ( A. x e. ~H ( ( S +op ( -u 1 .op T ) ) ` x ) = ( ( S -op T ) ` x ) <-> ( S +op ( -u 1 .op T ) ) = ( S -op T ) ) | 
						
							| 24 | 20 23 | mpbi |  |-  ( S +op ( -u 1 .op T ) ) = ( S -op T ) |