On January 16, 2008, a Ludao Airlines plane landed at Bingcheng Airport. As soon as it got off the plane, it entered the airport passage. The heating was on and it didn't feel cold at all.

"Hiss~~ The snow outside is so heavy!" Liu Yichen looked at the thick snow outside. Except for the airport runway that had no snow through special snow removal methods, the snow in other places was very thick. As you can imagine, the snow outside was very thick.

The coldness.

But this is an ice city, and the rivers will freeze. Isn’t it normal for heavy snow to fall?

Coming here, compared with southern cities such as Jinling and Rongcheng, Liu Yichen clearly felt the huge difference between the north and the south. The cold in the south is damp and cold. With or without heating, you feel cold everywhere, even if you hide under the quilt, you will feel cold.

; And the cold in the north means that it is cold outside. There are heaters in the house. If you don't go out, you won't feel the cold at all.

This is the difference in winter climate, followed by the huge gap in economics. Bingcheng is an old industrial base in Northeast China. It once played a decisive role in China's industrial sector. However, Liu Yichen now feels that the whole city is in a state of stagnation.

It doesn't have the economic vitality of the eastern seaboard.

Then he thought that in the next ten years or so, the three northeastern provinces would all be areas with a net population outflow across the country, Liu Yichen's eyes glowed with an unspeakable strange color.

You know, from the founding of the Republic to the present, the people in the three northeastern provinces have the highest level of education, ranking first in the country. This has never changed even more than ten years later. But now, with the regional economic downturn, employment here has always been

It is a question. You must know that there are too many state-owned enterprises in the three northeastern provinces. Many cities are even developed around a large state-owned enterprise. For example, Beichun City, where FAW is located, is a city that developed based on FAW.

Liu Yichen couldn't help but think of one of his netizens in the previous life. He originally studied at Yangzhou University, but later returned to Northeast China and couldn't find a job. He spent 200,000 to 300,000 yuan and worked as a teller in a bank. As a result, his monthly salary was 3,000 yuan.

, according to this income, it is only 36,000 yuan a year. Even if you don’t eat or drink, it will take nearly ten years to earn back the 20,000 to 30,000 yuan invested.

According to her, you can't find a decent job without spending money, and without a decent job, you can't find a decent partner either.

And for the three northeastern provinces, colleges and universities are actually very embarrassing. Last year, there were only one university in the top 100, Harbin Institute of Technology, ranked 13th, and Harbin Engineering University, ranked 80th.

There is no longer a top 100 university.

After boarding the bus arranged by the competition organizing committee, with the heating on, Liu Yichen sat in a seat at the back and looked outside all the way. The more he looked, the heavier his mood became, because he saw more, Ice City, a city in the northeast

The largest city in the three provinces, GDP reached 240 billion yuan last year, but there is no trace of the prosperity of Bingcheng. The dilapidated roads and houses look very ordinary. For Liu Yichen, the feeling is not even as good as that of Rongcheng. But you need to know that Rongcheng’s last year

GDP is less than 200 billion yuan.

Thinking of some more things, Liu Yichen couldn't help but secretly sigh. Under such circumstances, it is really not easy for Harbin Institute of Technology and Harbin Engineering to be the top in the country in some majors.

The bus arrived at a hotel not far from the Affiliated Middle School. This hotel was specially arranged by the competition organizing committee for 33 provincial teams and some mathematicians from all over the country.

The hotel arranged was good, it belongs to a star hotel.

Everyone was very excited after checking in and checking into the hotel, because except for Liu Yichen, very few of them could see the snow, so they didn't even bother to rest, so they went directly to an area outside the hotel to build a snowman with the children.

, having a snowball fight was a great time!

Liu Yichen wore a thick down jacket and went to the Harbin Institute of Technology across the street. There is an interesting thing about Harbin Institute of Technology, that is, people often confuse Harbin Engineering University with Harbin Institute of Technology. As a result of high scores, the college entrance examination application form was filled in as Harbin Engineering University, etc.

When I arrived in Bingcheng, I realized that Harbin Engineering University is Harbin Engineering University and Harbin Institute of Technology is Harbin Institute of Technology. For Fujian Province, this difference is just like the difference between Rongcheng University and Ludao University.

To be honest, the names of the universities in Bingcheng are quite similar, and it is easy to confuse people. Harbin Institute of Technology, Harbin Engineering University, Harbin Institute of Technology, Black Engineering, Black Technology. Every year, there are always students who doubt that this is the same school. But how can this be?

They are the same school, but they are very different from each other.

A very funny thing happened once. Harbin Institute of Technology was mistaken for Harbin Institute of Technology. A candidate from Qiongzhou Province scored 670 points in the college entrance examination and was successfully admitted to Harbin Institute of Technology. This candidate did not know the difference between Harbin Institute of Technology and Harbin Institute of Technology.

, thinking that Harbin Institute of Technology and Harbin Institute of Technology were the same university, they flew all the way from Qiongzhou Province to Bingcheng

, when he was about to get off the plane, he suddenly had an ominous premonition. The student felt that something was wrong. When he saw the admission notice to Harbin Institute of Technology, he felt something was wrong. He asked the flight attendant and found out that he was unlucky. The two were not the same.

Among the universities, Harbin Institute of Technology ranks 13th in the country, and Harbin Institute of Technology ranks 160th in the country. There is a huge difference between the two.

The icy and snowy Harbin Institute of Technology campus has a unique beauty. You can also see ice sculptures on the campus. There are very few pedestrians. Some are making snowmen, having snowball fights, and others are skating.

Liu Yichen is also lucky. Harbin Institute of Technology just held the Ice and Snow Culture Festival a few days ago. Colleges and universities from all over the country come here to carve ice sculptures, so there are many very beautiful ice sculptures on campus.

Suddenly, Liu Yichen stopped for a moment. He saw a girl dancing in the snow not far away, and Liu Yichen couldn't help but admire it.

Liu Yichen had to admit that Harbin Institute of Technology has its own unique heritage and humanistic atmosphere. It may not be as elegant as Southern University, but it has the magnificence of Northern China.

Arriving at the library of Harbin Institute of Technology, Liu Yichen found that there were many people in the library and there were no free seats. Every student was reading seriously...

"Sure enough... it's a typical polytechnic university, with more men and fewer women~~~" What Liu Yichen could see was that the ratio of men to women was very disparate, almost 4:1 or even 5:1. The number of boys

Far more than girls.

And how can I put it... the girls from Jinling University have better looks, while the girls from Harbin Institute of Technology generally have average looks.

Therefore, if Jinling University dares to use female students as a sign to recruit students in the future, it is because they have the confidence to do so.

After shopping around, Liu Yichen left Harbin Institute of Technology and returned to the hotel. He took a shower and changed into his pajamas, and then went to bed.

In the dream, Liu Yichen became a student of Harbin Institute of Technology, becoming an engineering boy, repairing machines with a wrench... Suddenly he dreamed of a girl hitting him with a wrench, and Liu Yichen woke up with a fright.

"Nah~~ It seems that I am not suitable for Harbin Institute of Technology~~" Liu Yichen secretly complained to himself, how could he have such a dream.

"Liu Yichen, do you know this question?" Huang Lengxiao asked.

Huang Lengxiao, from Licheng No. 5 Middle School, won second place in the provincial competition. He is a senior high school student and one year older than Liu Yichen.

"Let me see~~" Liu Yichen looked at the question. It was a geometric analysis question. Liu Yichen picked up the scratch paper and first drew the graph and corresponding points according to the conditions given in the question. Then he analyzed it and finally gave the proof.

.

Seeing the proof written by Liu Yichen, Huang Lengxiao couldn't help but suddenly realized. For them, the level difference between each other would not be too big, otherwise they would not be able to enter the provincial team. It was just that they did not know the steps to solve the problem. Seeing the solution

Then you will understand the steps of the question.

Liu Yichen took out a book of advanced mathematics from his bag and began to read it with interest. He had already mastered all the relevant knowledge of the Olympiad training materials. He began to study advanced mathematics. Advanced mathematics is divided into two volumes, with calculus as the core.

; The first volume introduces the object of calculus research - function, and the important basis of calculus research - limit theory. Once again, it basically establishes the concepts and theories of continuity, derivatives, differentials, indefinite integrals, and definite integrals of one-variable function calculus.

and applications, and introduces methods for solving differential equations.

The second volume introduces the basic concepts and theories of spatial analytic geometry and vector algebra, calculus of multivariate functions, and parts of infinite series.

What Liu Yichen is reading now is Volume 1 of Advanced Mathematics. He actually studied Advanced Mathematics in his last life, but unfortunately he didn't use it for many years and basically gave it back to his teacher. Now he just returns to his old profession and studies on his own.

I am also grateful that it is very easy to buy books nowadays. You can buy them directly from Xinhua Bookstore. Even if there is no book on site, you can wait a few days and it will be mailed to you.

Because he had solid mathematics knowledge in high school, Liu Yichen learned advanced mathematics much easier than in his previous life. He even learned a lot of knowledge that he had not been able to learn in his previous life.

It’s actually quite funny. Different people study the same book, but what they learn is actually very different. Some people can only learn superficial knowledge, while others can understand it deeply and learn from it.

It contains mathematical thinking logic, and mathematical thinking logic is the most precious thing.

Calculus at the high school level is actually very superficial, and the depth required by the college entrance examination is not deep. Therefore, high school teaching is also based on the difficulty of the college entrance examination, and it will not be taught too much or too detailed. But in higher education

The first two volumes of mathematics actually introduce calculus, and calculus is the core. The components of the two are completely different.

Of course, the two are not completely disconnected. On the contrary, they are very closely related. Only if you study high school mathematics well can you learn advanced mathematics well. High school mathematics is the foundation of advanced mathematics.

In fact, advanced mathematics is only a part of college mathematics. In addition, it includes advanced algebra, mathematical analysis, analytic geometry, probability theory, advanced geometry, differential geometry, functions of complex variables, functions of real variables, differential equations, and elementary mathematics.
Chapter completed!