| 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 | 10 12 | mpd |  | 
						
							| 14 | 13 | 3imp |  | 
						
							| 15 | 1 2 3 4 7 | rngonegmn1l |  | 
						
							| 16 | 15 | 3adant3 |  | 
						
							| 17 | 16 | oveq1d |  | 
						
							| 18 | 1 2 3 | rngocl |  | 
						
							| 19 | 18 | 3expb |  | 
						
							| 20 | 1 2 3 4 7 | rngonegmn1l |  | 
						
							| 21 | 19 20 | syldan |  | 
						
							| 22 | 21 | 3impb |  | 
						
							| 23 | 14 17 22 | 3eqtr4rd |  |