1. E’ vero che:                                        
   
   
2. E’ vero che:                                        
   
   
3. E’ vero che:                                        
   
4. E’ vero che:                                            
   
5. E’ vero che:                                              
   
6. E’ vero che:                                        
7. E' vero che:                                        
8. E’ vero che:                                        
9. E’ vero che:                                        
10. E’ vero che:                                        
11. E’ vero che:                                        
12. E’ vero che:                                               
    
     
13. E’ vero che:                                           
    
     
14. E’ vero che:                                              
    
     
15. E’ vero che:                                         3! × 4! = (3 × 4)! = 12!
    
     
16. E’ vero che:                                        
    
17. E’ vero che:                                        
    
18. E’ vero che:                                        
    
19. E’ vero che:                                           
    
     
20. E’ vero che:                                        

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