| Step | Hyp | Ref | Expression | 
						
							| 1 |  | znegcl | ⊢ ( 𝐷  ∈  ℤ  →  - 𝐷  ∈  ℤ ) | 
						
							| 2 |  | fzoaddel | ⊢ ( ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  ∧  - 𝐷  ∈  ℤ )  →  ( 𝐴  +  - 𝐷 )  ∈  ( ( 𝐵  +  - 𝐷 ) ..^ ( 𝐶  +  - 𝐷 ) ) ) | 
						
							| 3 | 1 2 | sylan2 | ⊢ ( ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  ∧  𝐷  ∈  ℤ )  →  ( 𝐴  +  - 𝐷 )  ∈  ( ( 𝐵  +  - 𝐷 ) ..^ ( 𝐶  +  - 𝐷 ) ) ) | 
						
							| 4 |  | elfzoelz | ⊢ ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  →  𝐴  ∈  ℤ ) | 
						
							| 5 | 4 | adantr | ⊢ ( ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  ∧  𝐷  ∈  ℤ )  →  𝐴  ∈  ℤ ) | 
						
							| 6 | 5 | zcnd | ⊢ ( ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  ∧  𝐷  ∈  ℤ )  →  𝐴  ∈  ℂ ) | 
						
							| 7 |  | simpr | ⊢ ( ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  ∧  𝐷  ∈  ℤ )  →  𝐷  ∈  ℤ ) | 
						
							| 8 | 7 | zcnd | ⊢ ( ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  ∧  𝐷  ∈  ℤ )  →  𝐷  ∈  ℂ ) | 
						
							| 9 | 6 8 | negsubd | ⊢ ( ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  ∧  𝐷  ∈  ℤ )  →  ( 𝐴  +  - 𝐷 )  =  ( 𝐴  −  𝐷 ) ) | 
						
							| 10 |  | elfzoel1 | ⊢ ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  →  𝐵  ∈  ℤ ) | 
						
							| 11 | 10 | adantr | ⊢ ( ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  ∧  𝐷  ∈  ℤ )  →  𝐵  ∈  ℤ ) | 
						
							| 12 | 11 | zcnd | ⊢ ( ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  ∧  𝐷  ∈  ℤ )  →  𝐵  ∈  ℂ ) | 
						
							| 13 | 12 8 | negsubd | ⊢ ( ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  ∧  𝐷  ∈  ℤ )  →  ( 𝐵  +  - 𝐷 )  =  ( 𝐵  −  𝐷 ) ) | 
						
							| 14 |  | elfzoel2 | ⊢ ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  →  𝐶  ∈  ℤ ) | 
						
							| 15 | 14 | adantr | ⊢ ( ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  ∧  𝐷  ∈  ℤ )  →  𝐶  ∈  ℤ ) | 
						
							| 16 | 15 | zcnd | ⊢ ( ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  ∧  𝐷  ∈  ℤ )  →  𝐶  ∈  ℂ ) | 
						
							| 17 | 16 8 | negsubd | ⊢ ( ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  ∧  𝐷  ∈  ℤ )  →  ( 𝐶  +  - 𝐷 )  =  ( 𝐶  −  𝐷 ) ) | 
						
							| 18 | 13 17 | oveq12d | ⊢ ( ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  ∧  𝐷  ∈  ℤ )  →  ( ( 𝐵  +  - 𝐷 ) ..^ ( 𝐶  +  - 𝐷 ) )  =  ( ( 𝐵  −  𝐷 ) ..^ ( 𝐶  −  𝐷 ) ) ) | 
						
							| 19 | 3 9 18 | 3eltr3d | ⊢ ( ( 𝐴  ∈  ( 𝐵 ..^ 𝐶 )  ∧  𝐷  ∈  ℤ )  →  ( 𝐴  −  𝐷 )  ∈  ( ( 𝐵  −  𝐷 ) ..^ ( 𝐶  −  𝐷 ) ) ) |