Focus on cultivating the thinking ability of simplifying the complex: According to the law of conservation of energy, the difficulty of the problem can be solved by decomposition (classification addition principle) and stratification (step-by-step multiplication principle).

Secondly, cultivate students' orderly thinking ability, tight seams, orderly analysis and problem-solving ability.

These are the thinking abilities that high school students must have.

How to learn permutation and combination well?

1, special treatment for special elements. For example, the problem of n digits with 0 can be divided into two categories: those with 0 and those without 0, and only need to determine the position of 0 when it contains 0. Another example: A and B are adjacent or not, and they can be arranged as big elements through local perfection.

2. Changes in the main attack direction. For example, the number of permutations and combinations is calculated by using the opposite event of event A, and the unqualified part is subtracted from the total to achieve the goal. Another example is to change the habitual thinking. When waiting in line or sitting, you can regard the position or stool as a' letter' and the person as a' mailbox', thus simplifying it.

3. The errors in calculating the number of permutations and combinations are usually nothing more than' repetition' and' omission'. It's good to check leaks and fill gaps, but it's important to subdivide openings. Determine the main line of subdivision-it is conducive to classification or division and has a broad outline. This requires higher quality of thinking. We are growing up in setbacks and setbacks.

In short, learning' permutation and combination' makes us smarter!