Database ZF (ZERMELO-FRAENKEL) SET THEORY ZF Set Theory - add the Axiom of Power Sets Founded and well-ordering relations nfse  
				
		 
		
			
		 
		Description:   Bound-variable hypothesis builder for set-like relations.  (Contributed by Mario Carneiro , 24-Jun-2015)   (Revised by Mario Carneiro , 14-Oct-2016) 
		
			
				
					Ref 
					Expression 
				 
					
						Hypotheses 
						nffr.r   ⊢    Ⅎ   _  x  R       
					 
					
						nffr.a   ⊢    Ⅎ   _  x  A       
					 
				
					Assertion 
					nfse   ⊢   Ⅎ  x   R  Se  A         
				 
			
		 
		
				Proof 
				
					
						Step 
						Hyp 
						Ref 
						Expression 
					 
						
							1 
								
							 
							nffr.r  ⊢    Ⅎ   _  x  R       
						
							2 
								
							 
							nffr.a  ⊢    Ⅎ   _  x  A       
						
							3 
								
							 
							df-se   ⊢   R  Se  A    ↔   ∀  b  ∈  A    a  ∈  A  |  a  R  b   ∈  V           
						
							4 
								
							 
							nfcv  ⊢    Ⅎ   _  x  a       
						
							5 
								
							 
							nfcv  ⊢    Ⅎ   _  x  b       
						
							6 
								4  1  5 
							 
							nfbr  ⊢   Ⅎ  x  a  R  b      
						
							7 
								6  2 
							 
							nfrabw  ⊢    Ⅎ   _  x   a  ∈  A  |  a  R  b        
						
							8 
								7 
							 
							nfel1  ⊢   Ⅎ  x    a  ∈  A  |  a  R  b   ∈  V         
						
							9 
								2  8 
							 
							nfralw  ⊢   Ⅎ  x   ∀  b  ∈  A    a  ∈  A  |  a  R  b   ∈  V           
						
							10 
								3  9 
							 
							nfxfr  ⊢   Ⅎ  x   R  Se  A