Methods: Just exchange three lines of numbers casually, and ensure that the sum of each line is 2 100. For example:

1、800, 1300。

1000, 1 100。

900, 1200。

2、800, 1000。

1 100, 1300。

1200,900。

Looking for the meaning of fill-in-the-blank rules

In fact, it is to strengthen the understanding of the general law of sequence. Although there are many solutions, it is mainly to cultivate the ability to discover the general law of series and guess the general term of series (that is, the ability to use incomplete induction).

So that when we encounter some series whose general terms are difficult to find by general methods, we can quickly and accurately guess the general term formula of this series through the first few terms, and then prove it by mathematical induction or reduction to absurdity or other methods, bypassing the main mountain and quickly getting its general term formula.