| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							prn0 | 
							⊢ ( 𝐵  ∈  P  →  𝐵  ≠  ∅ )  | 
						
						
							| 2 | 
							
								
							 | 
							n0 | 
							⊢ ( 𝐵  ≠  ∅  ↔  ∃ 𝑦 𝑦  ∈  𝐵 )  | 
						
						
							| 3 | 
							
								1 2
							 | 
							sylib | 
							⊢ ( 𝐵  ∈  P  →  ∃ 𝑦 𝑦  ∈  𝐵 )  | 
						
						
							| 4 | 
							
								3
							 | 
							adantl | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ∃ 𝑦 𝑦  ∈  𝐵 )  | 
						
						
							| 5 | 
							
								
							 | 
							addclpr | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ( 𝐴  +P  𝐵 )  ∈  P )  | 
						
						
							| 6 | 
							
								
							 | 
							df-plp | 
							⊢  +P   =  ( 𝑤  ∈  P ,  𝑣  ∈  P  ↦  { 𝑥  ∣  ∃ 𝑦  ∈  𝑤 ∃ 𝑧  ∈  𝑣 𝑥  =  ( 𝑦  +Q  𝑧 ) } )  | 
						
						
							| 7 | 
							
								
							 | 
							addclnq | 
							⊢ ( ( 𝑦  ∈  Q  ∧  𝑧  ∈  Q )  →  ( 𝑦  +Q  𝑧 )  ∈  Q )  | 
						
						
							| 8 | 
							
								6 7
							 | 
							genpprecl | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ( ( 𝑥  ∈  𝐴  ∧  𝑦  ∈  𝐵 )  →  ( 𝑥  +Q  𝑦 )  ∈  ( 𝐴  +P  𝐵 ) ) )  | 
						
						
							| 9 | 
							
								8
							 | 
							imp | 
							⊢ ( ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  ∧  ( 𝑥  ∈  𝐴  ∧  𝑦  ∈  𝐵 ) )  →  ( 𝑥  +Q  𝑦 )  ∈  ( 𝐴  +P  𝐵 ) )  | 
						
						
							| 10 | 
							
								
							 | 
							elprnq | 
							⊢ ( ( ( 𝐴  +P  𝐵 )  ∈  P  ∧  ( 𝑥  +Q  𝑦 )  ∈  ( 𝐴  +P  𝐵 ) )  →  ( 𝑥  +Q  𝑦 )  ∈  Q )  | 
						
						
							| 11 | 
							
								
							 | 
							addnqf | 
							⊢  +Q  : ( Q  ×  Q ) ⟶ Q  | 
						
						
							| 12 | 
							
								11
							 | 
							fdmi | 
							⊢ dom   +Q   =  ( Q  ×  Q )  | 
						
						
							| 13 | 
							
								
							 | 
							0nnq | 
							⊢ ¬  ∅  ∈  Q  | 
						
						
							| 14 | 
							
								12 13
							 | 
							ndmovrcl | 
							⊢ ( ( 𝑥  +Q  𝑦 )  ∈  Q  →  ( 𝑥  ∈  Q  ∧  𝑦  ∈  Q ) )  | 
						
						
							| 15 | 
							
								
							 | 
							ltaddnq | 
							⊢ ( ( 𝑥  ∈  Q  ∧  𝑦  ∈  Q )  →  𝑥  <Q  ( 𝑥  +Q  𝑦 ) )  | 
						
						
							| 16 | 
							
								10 14 15
							 | 
							3syl | 
							⊢ ( ( ( 𝐴  +P  𝐵 )  ∈  P  ∧  ( 𝑥  +Q  𝑦 )  ∈  ( 𝐴  +P  𝐵 ) )  →  𝑥  <Q  ( 𝑥  +Q  𝑦 ) )  | 
						
						
							| 17 | 
							
								
							 | 
							prcdnq | 
							⊢ ( ( ( 𝐴  +P  𝐵 )  ∈  P  ∧  ( 𝑥  +Q  𝑦 )  ∈  ( 𝐴  +P  𝐵 ) )  →  ( 𝑥  <Q  ( 𝑥  +Q  𝑦 )  →  𝑥  ∈  ( 𝐴  +P  𝐵 ) ) )  | 
						
						
							| 18 | 
							
								16 17
							 | 
							mpd | 
							⊢ ( ( ( 𝐴  +P  𝐵 )  ∈  P  ∧  ( 𝑥  +Q  𝑦 )  ∈  ( 𝐴  +P  𝐵 ) )  →  𝑥  ∈  ( 𝐴  +P  𝐵 ) )  | 
						
						
							| 19 | 
							
								5 9 18
							 | 
							syl2an2r | 
							⊢ ( ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  ∧  ( 𝑥  ∈  𝐴  ∧  𝑦  ∈  𝐵 ) )  →  𝑥  ∈  ( 𝐴  +P  𝐵 ) )  | 
						
						
							| 20 | 
							
								19
							 | 
							exp32 | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ( 𝑥  ∈  𝐴  →  ( 𝑦  ∈  𝐵  →  𝑥  ∈  ( 𝐴  +P  𝐵 ) ) ) )  | 
						
						
							| 21 | 
							
								20
							 | 
							com23 | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ( 𝑦  ∈  𝐵  →  ( 𝑥  ∈  𝐴  →  𝑥  ∈  ( 𝐴  +P  𝐵 ) ) ) )  | 
						
						
							| 22 | 
							
								21
							 | 
							alrimdv | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ( 𝑦  ∈  𝐵  →  ∀ 𝑥 ( 𝑥  ∈  𝐴  →  𝑥  ∈  ( 𝐴  +P  𝐵 ) ) ) )  | 
						
						
							| 23 | 
							
								
							 | 
							df-ss | 
							⊢ ( 𝐴  ⊆  ( 𝐴  +P  𝐵 )  ↔  ∀ 𝑥 ( 𝑥  ∈  𝐴  →  𝑥  ∈  ( 𝐴  +P  𝐵 ) ) )  | 
						
						
							| 24 | 
							
								22 23
							 | 
							imbitrrdi | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ( 𝑦  ∈  𝐵  →  𝐴  ⊆  ( 𝐴  +P  𝐵 ) ) )  | 
						
						
							| 25 | 
							
								
							 | 
							vex | 
							⊢ 𝑦  ∈  V  | 
						
						
							| 26 | 
							
								25
							 | 
							prlem934 | 
							⊢ ( 𝐴  ∈  P  →  ∃ 𝑥  ∈  𝐴 ¬  ( 𝑥  +Q  𝑦 )  ∈  𝐴 )  | 
						
						
							| 27 | 
							
								26
							 | 
							adantr | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ∃ 𝑥  ∈  𝐴 ¬  ( 𝑥  +Q  𝑦 )  ∈  𝐴 )  | 
						
						
							| 28 | 
							
								
							 | 
							eleq2 | 
							⊢ ( 𝐴  =  ( 𝐴  +P  𝐵 )  →  ( ( 𝑥  +Q  𝑦 )  ∈  𝐴  ↔  ( 𝑥  +Q  𝑦 )  ∈  ( 𝐴  +P  𝐵 ) ) )  | 
						
						
							| 29 | 
							
								28
							 | 
							biimprcd | 
							⊢ ( ( 𝑥  +Q  𝑦 )  ∈  ( 𝐴  +P  𝐵 )  →  ( 𝐴  =  ( 𝐴  +P  𝐵 )  →  ( 𝑥  +Q  𝑦 )  ∈  𝐴 ) )  | 
						
						
							| 30 | 
							
								29
							 | 
							con3d | 
							⊢ ( ( 𝑥  +Q  𝑦 )  ∈  ( 𝐴  +P  𝐵 )  →  ( ¬  ( 𝑥  +Q  𝑦 )  ∈  𝐴  →  ¬  𝐴  =  ( 𝐴  +P  𝐵 ) ) )  | 
						
						
							| 31 | 
							
								8 30
							 | 
							syl6 | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ( ( 𝑥  ∈  𝐴  ∧  𝑦  ∈  𝐵 )  →  ( ¬  ( 𝑥  +Q  𝑦 )  ∈  𝐴  →  ¬  𝐴  =  ( 𝐴  +P  𝐵 ) ) ) )  | 
						
						
							| 32 | 
							
								31
							 | 
							expd | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ( 𝑥  ∈  𝐴  →  ( 𝑦  ∈  𝐵  →  ( ¬  ( 𝑥  +Q  𝑦 )  ∈  𝐴  →  ¬  𝐴  =  ( 𝐴  +P  𝐵 ) ) ) ) )  | 
						
						
							| 33 | 
							
								32
							 | 
							com34 | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ( 𝑥  ∈  𝐴  →  ( ¬  ( 𝑥  +Q  𝑦 )  ∈  𝐴  →  ( 𝑦  ∈  𝐵  →  ¬  𝐴  =  ( 𝐴  +P  𝐵 ) ) ) ) )  | 
						
						
							| 34 | 
							
								33
							 | 
							rexlimdv | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ( ∃ 𝑥  ∈  𝐴 ¬  ( 𝑥  +Q  𝑦 )  ∈  𝐴  →  ( 𝑦  ∈  𝐵  →  ¬  𝐴  =  ( 𝐴  +P  𝐵 ) ) ) )  | 
						
						
							| 35 | 
							
								27 34
							 | 
							mpd | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ( 𝑦  ∈  𝐵  →  ¬  𝐴  =  ( 𝐴  +P  𝐵 ) ) )  | 
						
						
							| 36 | 
							
								24 35
							 | 
							jcad | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ( 𝑦  ∈  𝐵  →  ( 𝐴  ⊆  ( 𝐴  +P  𝐵 )  ∧  ¬  𝐴  =  ( 𝐴  +P  𝐵 ) ) ) )  | 
						
						
							| 37 | 
							
								
							 | 
							dfpss2 | 
							⊢ ( 𝐴  ⊊  ( 𝐴  +P  𝐵 )  ↔  ( 𝐴  ⊆  ( 𝐴  +P  𝐵 )  ∧  ¬  𝐴  =  ( 𝐴  +P  𝐵 ) ) )  | 
						
						
							| 38 | 
							
								36 37
							 | 
							imbitrrdi | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ( 𝑦  ∈  𝐵  →  𝐴  ⊊  ( 𝐴  +P  𝐵 ) ) )  | 
						
						
							| 39 | 
							
								38
							 | 
							exlimdv | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ( ∃ 𝑦 𝑦  ∈  𝐵  →  𝐴  ⊊  ( 𝐴  +P  𝐵 ) ) )  | 
						
						
							| 40 | 
							
								4 39
							 | 
							mpd | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  𝐴  ⊊  ( 𝐴  +P  𝐵 ) )  | 
						
						
							| 41 | 
							
								
							 | 
							ltprord | 
							⊢ ( ( 𝐴  ∈  P  ∧  ( 𝐴  +P  𝐵 )  ∈  P )  →  ( 𝐴 <P  ( 𝐴  +P  𝐵 )  ↔  𝐴  ⊊  ( 𝐴  +P  𝐵 ) ) )  | 
						
						
							| 42 | 
							
								5 41
							 | 
							syldan | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  ( 𝐴 <P  ( 𝐴  +P  𝐵 )  ↔  𝐴  ⊊  ( 𝐴  +P  𝐵 ) ) )  | 
						
						
							| 43 | 
							
								40 42
							 | 
							mpbird | 
							⊢ ( ( 𝐴  ∈  P  ∧  𝐵  ∈  P )  →  𝐴 <P  ( 𝐴  +P  𝐵 ) )  |