Chapter 290 (1/2)
Chapter 293
the national high school mathematics league, the content of the test questions mainly covers four branches of Mathematics: plane geometry, algebra, elementary number theory, combinatorial mathematics.
Of course, it is not only the mathematics competition, but also the main test contents of these four aspects in IMO. However, it is not limited to a certain type of problem, which must be solved with some knowledge. Mathematics is an inter related discipline. A problem can be solved by algebra or number theory. Mathematics is always full of infinite possibilities and endless fun.
For ordinary people, the formula that makes you feel big at a glance may have a different aesthetic feeling for this group of students participating in competition training.
…………
On the platform, old Tang held up his book and wrote down the title on the blackboard.
[given a positive integer n, each of the six vertices of a positive hexagon has a nonnegative integer, and its sum is n. now, do the following operations: erase the number on a vertex, and then write the absolute value of the difference between the numbers on the adjacent two vertices, and calculate all N, so that no matter what integers are in the beginning, a series of operations can be carried out to make the number on each vertex be zero. 】
from the point of view of the title, this topic is not simple, and it is quite different from various types of questions encountered in high school. It's no wonder that only one of the more than 30 people who participated in the training came out.
Comrade Tang wrote the steps on the blackboard while he was explaining them to the audience.
He first drew a regular hexagon.
”First of all, according to the meaning of the title, we assume that the parity of the six points of a hexagon is even, odd, odd, even, odd, odd, odd. In this way, no matter how you operate, the parity of these six numbers will not change. So
“…… According to the above process, we can get a proposition for the time being: as long as the initial six numbers are not even, odd, odd, even, odd, odd, and not all even, then we can make all numbers equal to zero through finite operations
”This proposition is only written by ourselves, and we don't know whether it is true or false. Next, we need to prove that this proposition is a true proposition through classified discussion. According to my discussion steps, we will start from...”
“…… Do you understand the process on this blackboard? If you understand it, I will clean it Next, we will discuss the case of | a2-a6 | = K. since 0 ≤ A2, A6 ≤ K, we may as well assume... ”
Click! CLICK!
The two blackboards were rubbed twice by Lao Tang. It took him about half an hour to write dozens of lines of dense formulas. It took him about half an hour to prove the complicated topic in terms of thinking and process.
As long as two-thirds of the students who participate in the training are still in a state of muddle up to now.
Who am I? Where am i? Why am I here for this training?
After three companies, they all looked at the short boy in the front row. His name is Chen Gong. He has been stable in the first place of his age. He has a good Xueba. It is also the only student who has solved this complicated and incomparable problem among more than 30 people.
Some people say that maybe Chen Gong will be the second student to become No.1 in the college entrance examination after Cheng Nuo of Qingcheng No.2 Middle School.
The great God is the great God. It's really not a group of ordinary people can compare with!
In the eyes of all the people, Chen Gong did not show any pride.
To be honest, he only thinks that this is a very basic operation. His goal in the future is to win the first prize of several League, enter the national team and win IMO gold medal.
After talking for such a long time, Comrade Tang was also a bit dry. He unscrewed the lid of the thermos cup on the lecture table, took a sip, held his hands on the table, and habitually asked, ”do you have any questions about this question? If not, then we... ”