Because 1 multiplied by any number is itself; 2 times any number ends with 2; 5 times any number ends in 0 or 5, which does not match.

And this space is definitely relatively small, only 3 and 4.

Considering the multiplication of the first space and the fifth space, the result can only be less than ten. The first space can only be 2 or 1.

Because of the particularity of 5, the fourth one is empty.

Considering the combination of 1, 2, 3 and 4 respectively, the possible values of the first place are

1 and 3: 3,4,5

1 and 4: 4, 5, 6, 7

2 and 3: 6, 7, 8

2 and 4: 8, 9

(For example, 1000*3=3000, while 1900*3=5700, the same principle can also be applied to the other three combinations. Therefore, the spatial scope of the sixth empty space is also reduced accordingly. )

Starting from the fourth and fifth blank spaces and pushing to the third blank space, all used numbers will be erased, and the added numbers will be subtracted when selecting adjacent numbers.

Give each group a chance. In the process of trying, you will find that unreasonable projects are obvious. If you quickly eliminate them, you will get the following formula:

1738*4=6952