| Step | Hyp | Ref | Expression | 
						
							| 1 |  | ringnegmul.1 |  | 
						
							| 2 |  | ringnegmul.2 |  | 
						
							| 3 |  | ringnegmul.3 |  | 
						
							| 4 |  | ringnegmul.4 |  | 
						
							| 5 | 1 | rneqi |  | 
						
							| 6 | 3 5 | eqtri |  | 
						
							| 7 |  | eqid |  | 
						
							| 8 | 6 2 7 | rngo1cl |  | 
						
							| 9 | 1 3 4 | rngonegcl |  | 
						
							| 10 | 8 9 | mpdan |  | 
						
							| 11 | 1 2 3 | rngoass |  | 
						
							| 12 | 11 | 3exp2 |  | 
						
							| 13 | 12 | com24 |  | 
						
							| 14 | 13 | com34 |  | 
						
							| 15 | 10 14 | mpd |  | 
						
							| 16 | 15 | 3imp |  | 
						
							| 17 | 1 2 3 | rngocl |  | 
						
							| 18 | 17 | 3expb |  | 
						
							| 19 | 1 2 3 4 7 | rngonegmn1r |  | 
						
							| 20 | 18 19 | syldan |  | 
						
							| 21 | 20 | 3impb |  | 
						
							| 22 | 1 2 3 4 7 | rngonegmn1r |  | 
						
							| 23 | 22 | 3adant2 |  | 
						
							| 24 | 23 | oveq2d |  | 
						
							| 25 | 16 21 24 | 3eqtr4d |  |