The formula of dislocation rearrangement is: dn = (n-1) (dn-1+dn-2), where D 1=0, D2= 1, D3=2, D4=9 and D5=44.

To understand dislocation rearrangement, let's look at a simple example: three pigeons correspond to their own pigeon cages. One day, every pigeon did not fly into its cage, and every pigeon did not return to its "home". There are three pigeons named A, B and C, and their cages are A, B and C respectively. The requirement of the topic is actually interconnection, but A-a, B-b, C-.

explain

First,? At dinner, each of the four chefs cooked a special dish. Now everyone is required to taste a dish, but they can't taste their own cooking. Q * * * has several different ways of tasting.

Analysis: the title requires four chefs to taste the dishes, but each chef can't taste his own dishes, which is in line with the dislocation rearrangement model. The solution is D4, and D4=9 can be obtained by using the formula or directly looking up the data summarized above.

2. Five branches of a group enterprise send one person to the group headquarters for training, and then five people are randomly assigned to these five branches after training. Only 1 person was assigned to each branch. There are several ways to ask five people who participated in the training, and only 1 returned to the original company after the training.

Analysis: There are five people in this question, but in the end only one person returned to the original company, so first choose 1 person from these five people to return to the original company, and then rearrange four people. The result is = c (1, 5) × 9 = 45.