theorem znegb1 (n: nat): $ -uZ b1 n = b0 (suc n) $;
    
      
        | Step | Hyp | Ref | Expression | 
|---|
        
          | 1 |  | eqtr | -uZ b1 n = b0 (zsnd (b1 n) - zfst (b1 n)) -> b0 (zsnd (b1 n) - zfst (b1 n)) = b0 (suc n) -> -uZ b1 n = b0 (suc n) | 
        
          | 2 |  | znsubpos | zfst (b1 n) <= zsnd (b1 n) -> zsnd (b1 n) -ZN zfst (b1 n) = b0 (zsnd (b1 n) - zfst (b1 n)) | 
        
          | 3 | 2 | conv zneg | zfst (b1 n) <= zsnd (b1 n) -> -uZ b1 n = b0 (zsnd (b1 n) - zfst (b1 n)) | 
        
          | 4 |  | leeq1 | zfst (b1 n) = 0 -> (zfst (b1 n) <= zsnd (b1 n) <-> 0 <= zsnd (b1 n)) | 
        
          | 5 |  | zfstb1 | zfst (b1 n) = 0 | 
        
          | 6 | 4, 5 | ax_mp | zfst (b1 n) <= zsnd (b1 n) <-> 0 <= zsnd (b1 n) | 
        
          | 7 |  | le01 | 0 <= zsnd (b1 n) | 
        
          | 8 | 6, 7 | mpbir | zfst (b1 n) <= zsnd (b1 n) | 
        
          | 9 | 3, 8 | ax_mp | -uZ b1 n = b0 (zsnd (b1 n) - zfst (b1 n)) | 
        
          | 10 | 1, 9 | ax_mp | b0 (zsnd (b1 n) - zfst (b1 n)) = b0 (suc n) -> -uZ b1 n = b0 (suc n) | 
        
          | 11 |  | b0eq | zsnd (b1 n) - zfst (b1 n) = suc n -> b0 (zsnd (b1 n) - zfst (b1 n)) = b0 (suc n) | 
        
          | 12 |  | eqtr | zsnd (b1 n) - zfst (b1 n) = suc n - 0 -> suc n - 0 = suc n -> zsnd (b1 n) - zfst (b1 n) = suc n | 
        
          | 13 |  | subeq | zsnd (b1 n) = suc n -> zfst (b1 n) = 0 -> zsnd (b1 n) - zfst (b1 n) = suc n - 0 | 
        
          | 14 |  | zsndb1 | zsnd (b1 n) = suc n | 
        
          | 15 | 13, 14 | ax_mp | zfst (b1 n) = 0 -> zsnd (b1 n) - zfst (b1 n) = suc n - 0 | 
        
          | 16 | 15, 5 | ax_mp | zsnd (b1 n) - zfst (b1 n) = suc n - 0 | 
        
          | 17 | 12, 16 | ax_mp | suc n - 0 = suc n -> zsnd (b1 n) - zfst (b1 n) = suc n | 
        
          | 18 |  | sub02 | suc n - 0 = suc n | 
        
          | 19 | 17, 18 | ax_mp | zsnd (b1 n) - zfst (b1 n) = suc n | 
        
          | 20 | 11, 19 | ax_mp | b0 (zsnd (b1 n) - zfst (b1 n)) = b0 (suc n) | 
        
          | 21 | 10, 20 | ax_mp | -uZ b1 n = b0 (suc n) | 
      
    
    Axiom use
    axs_prop_calc
     (ax_1,
      ax_2,
      ax_3,
      ax_mp,
      itru),
    
axs_pred_calc
     (ax_gen,
      ax_4,
      ax_5,
      ax_6,
      ax_7,
      ax_10,
      ax_11,
      ax_12),
    
axs_set
     (elab,
      ax_8),
    
axs_the
     (theid,
      the0),
    
axs_peano
     (peano1,
      peano2,
      peano5,
      addeq,
      muleq,
      add0,
      addS,
      mul0,
      mulS)