A ∩ B = {1, 2,3}, Yizhi A = {1, 2,3, ...}, B = {1, 2,3, ...}

Because A and B are I = {1, 2,3, ..., 9}, it can be known that the elements of sets A and B take the combination number of any number of elements in I except 1, 2,3, that is,

Taking out any number of elements other than 1, 2 and 3 from I means taking out 0-6 numbers (***6 numbers) from 4-9. According to the principle of combination, we can know that * * has.

0, 1 method

The method of taking 1 6.

Take the method of 2, 15.

Take the method of 3 and 20.

Take the method of 4, 15.

Take five or six methods.

Take 6, 1 method.

* * * There are 64 methods. Since A and B can adopt any of these 64 methods,

So the number of good sets is n=64*64=4096.