1, with serial number.

To find a regular topic, we usually give a series of quantities in a certain order, which requires us to find a universal law according to these known quantities. Find out the rule, usually the serial number of the package. Therefore, it is easier to find the mystery by comparing variables with serial numbers.

2. Look at the increase

If the increase is equal (actually arithmetic progression): Compare each number with its previous number. If the increments are equal, the nth number can be expressed as al+(n- 1)b, where a 1 is the first digit of the sequence, b is the increment, and (n- 1)b is the sum of the first digit to the nth digit. Then simplify the algebraic expression a1+(n-1) b.

If the increments are not equal, but the increments increase by the same amount (that is, the increments are equal, that is, the secondary arithmetic progression). If the growth rates are 3, 5, 7 and 9 respectively, it means that the growth rate has increased by the same amount. The number of the nth bit of this series also has a general solution.

3. Holistic thinking

From the specific practical problems, observe the characteristics of each quantity and the changing law between them; From here to there, make reasonable associations and make bold guesses; Good at analogy, looking for similarities or similarities from different things;

Summarize the law, draw a conclusion and verify whether the conclusion is correct or not; Being good at changing the way of thinking, getting twice the result with half the effort, and exploring the law is a kind of thinking activity, which is a leap from expert to semi-expert, and requires certain inductive and comprehensive ability. When there are multiple sets of known data, it is necessary to observe carefully and compare repeatedly to find out the law accurately.