| Step | Hyp | Ref | Expression | 
						
							| 1 |  | suppss2f.p | ⊢ Ⅎ 𝑘 𝜑 | 
						
							| 2 |  | suppss2f.a | ⊢ Ⅎ 𝑘 𝐴 | 
						
							| 3 |  | suppss2f.w | ⊢ Ⅎ 𝑘 𝑊 | 
						
							| 4 |  | suppss2f.n | ⊢ ( ( 𝜑  ∧  𝑘  ∈  ( 𝐴  ∖  𝑊 ) )  →  𝐵  =  𝑍 ) | 
						
							| 5 |  | suppss2f.v | ⊢ ( 𝜑  →  𝐴  ∈  𝑉 ) | 
						
							| 6 |  | nfcv | ⊢ Ⅎ 𝑙 𝐴 | 
						
							| 7 |  | nfcv | ⊢ Ⅎ 𝑙 𝐵 | 
						
							| 8 |  | nfcsb1v | ⊢ Ⅎ 𝑘 ⦋ 𝑙  /  𝑘 ⦌ 𝐵 | 
						
							| 9 |  | csbeq1a | ⊢ ( 𝑘  =  𝑙  →  𝐵  =  ⦋ 𝑙  /  𝑘 ⦌ 𝐵 ) | 
						
							| 10 | 2 6 7 8 9 | cbvmptf | ⊢ ( 𝑘  ∈  𝐴  ↦  𝐵 )  =  ( 𝑙  ∈  𝐴  ↦  ⦋ 𝑙  /  𝑘 ⦌ 𝐵 ) | 
						
							| 11 | 10 | oveq1i | ⊢ ( ( 𝑘  ∈  𝐴  ↦  𝐵 )  supp  𝑍 )  =  ( ( 𝑙  ∈  𝐴  ↦  ⦋ 𝑙  /  𝑘 ⦌ 𝐵 )  supp  𝑍 ) | 
						
							| 12 | 4 | sbt | ⊢ [ 𝑙  /  𝑘 ] ( ( 𝜑  ∧  𝑘  ∈  ( 𝐴  ∖  𝑊 ) )  →  𝐵  =  𝑍 ) | 
						
							| 13 |  | sbim | ⊢ ( [ 𝑙  /  𝑘 ] ( ( 𝜑  ∧  𝑘  ∈  ( 𝐴  ∖  𝑊 ) )  →  𝐵  =  𝑍 )  ↔  ( [ 𝑙  /  𝑘 ] ( 𝜑  ∧  𝑘  ∈  ( 𝐴  ∖  𝑊 ) )  →  [ 𝑙  /  𝑘 ] 𝐵  =  𝑍 ) ) | 
						
							| 14 |  | sban | ⊢ ( [ 𝑙  /  𝑘 ] ( 𝜑  ∧  𝑘  ∈  ( 𝐴  ∖  𝑊 ) )  ↔  ( [ 𝑙  /  𝑘 ] 𝜑  ∧  [ 𝑙  /  𝑘 ] 𝑘  ∈  ( 𝐴  ∖  𝑊 ) ) ) | 
						
							| 15 | 1 | sbf | ⊢ ( [ 𝑙  /  𝑘 ] 𝜑  ↔  𝜑 ) | 
						
							| 16 | 2 3 | nfdif | ⊢ Ⅎ 𝑘 ( 𝐴  ∖  𝑊 ) | 
						
							| 17 | 16 | clelsb1fw | ⊢ ( [ 𝑙  /  𝑘 ] 𝑘  ∈  ( 𝐴  ∖  𝑊 )  ↔  𝑙  ∈  ( 𝐴  ∖  𝑊 ) ) | 
						
							| 18 | 15 17 | anbi12i | ⊢ ( ( [ 𝑙  /  𝑘 ] 𝜑  ∧  [ 𝑙  /  𝑘 ] 𝑘  ∈  ( 𝐴  ∖  𝑊 ) )  ↔  ( 𝜑  ∧  𝑙  ∈  ( 𝐴  ∖  𝑊 ) ) ) | 
						
							| 19 | 14 18 | bitri | ⊢ ( [ 𝑙  /  𝑘 ] ( 𝜑  ∧  𝑘  ∈  ( 𝐴  ∖  𝑊 ) )  ↔  ( 𝜑  ∧  𝑙  ∈  ( 𝐴  ∖  𝑊 ) ) ) | 
						
							| 20 |  | sbsbc | ⊢ ( [ 𝑙  /  𝑘 ] 𝐵  =  𝑍  ↔  [ 𝑙  /  𝑘 ] 𝐵  =  𝑍 ) | 
						
							| 21 |  | sbceq1g | ⊢ ( 𝑙  ∈  V  →  ( [ 𝑙  /  𝑘 ] 𝐵  =  𝑍  ↔  ⦋ 𝑙  /  𝑘 ⦌ 𝐵  =  𝑍 ) ) | 
						
							| 22 | 21 | elv | ⊢ ( [ 𝑙  /  𝑘 ] 𝐵  =  𝑍  ↔  ⦋ 𝑙  /  𝑘 ⦌ 𝐵  =  𝑍 ) | 
						
							| 23 | 20 22 | bitri | ⊢ ( [ 𝑙  /  𝑘 ] 𝐵  =  𝑍  ↔  ⦋ 𝑙  /  𝑘 ⦌ 𝐵  =  𝑍 ) | 
						
							| 24 | 19 23 | imbi12i | ⊢ ( ( [ 𝑙  /  𝑘 ] ( 𝜑  ∧  𝑘  ∈  ( 𝐴  ∖  𝑊 ) )  →  [ 𝑙  /  𝑘 ] 𝐵  =  𝑍 )  ↔  ( ( 𝜑  ∧  𝑙  ∈  ( 𝐴  ∖  𝑊 ) )  →  ⦋ 𝑙  /  𝑘 ⦌ 𝐵  =  𝑍 ) ) | 
						
							| 25 | 13 24 | bitri | ⊢ ( [ 𝑙  /  𝑘 ] ( ( 𝜑  ∧  𝑘  ∈  ( 𝐴  ∖  𝑊 ) )  →  𝐵  =  𝑍 )  ↔  ( ( 𝜑  ∧  𝑙  ∈  ( 𝐴  ∖  𝑊 ) )  →  ⦋ 𝑙  /  𝑘 ⦌ 𝐵  =  𝑍 ) ) | 
						
							| 26 | 12 25 | mpbi | ⊢ ( ( 𝜑  ∧  𝑙  ∈  ( 𝐴  ∖  𝑊 ) )  →  ⦋ 𝑙  /  𝑘 ⦌ 𝐵  =  𝑍 ) | 
						
							| 27 | 26 5 | suppss2 | ⊢ ( 𝜑  →  ( ( 𝑙  ∈  𝐴  ↦  ⦋ 𝑙  /  𝑘 ⦌ 𝐵 )  supp  𝑍 )  ⊆  𝑊 ) | 
						
							| 28 | 11 27 | eqsstrid | ⊢ ( 𝜑  →  ( ( 𝑘  ∈  𝐴  ↦  𝐵 )  supp  𝑍 )  ⊆  𝑊 ) |