Generally, we should observe the characteristics first, and then check several commonly used methods in turn, such as the difference and the operational relationship between adjacent three items. If the number changes dramatically, you can consider the square sum cube, and be familiar with some commonly used square sum cube values. Doing more will enhance self-confidence and experience.

You can use the following methods:

Fibonacci sequence method: each number is the sum of the first two numbers.

Arithmetic series method: the difference between every two numbers is equal.

"Skip" method: You can look at it every once in a while to see what the relationship between the separated numbers is, for example, 14, 1,12,3,10,5, odd items become arithmetic progression, even items also become arithmetic progression, and then you have to fill in 8.

Incremental method: See whether the difference between every two numbers is arithmetic progression, such as 1, 4, 8, 13, 19. The difference between every two numbers is 3, 4, 5 and 6, so the next difference should be 7, which is 26.

Decomposition method: decompose each number to see what the law is. For example, 1 4 9 16 ()

2 6 12 20( )

3 15 35 63( ),

After decomposition, 1× 1 2×2 3×3 4×4 was obtained.

1×2 2×3 3×4 4×5

1×3 3×5 5×7 7×9,

That is, the nth number of the first row is n 2, the nth number of the second row is n×(n+ 1), and the nth number of the third row is the nth positive odd number ×(n+2), so the answer is 25,30,99.