Chapter 143 Yes, that’s it!

The next day, early morning, Shaoyuan Canteen.

"I thought for a long time last night, I am definitely not a math genius. Because I am different from you, and I am different from that man.

For example, you can easily get full marks in high school math, but I can't. I often make mistakes, both before and now.

And I can't be as shameless as you at my age. So don't expect me to say nice things in front of Academician Yuan like you and Coco did.

If Academician Yuan asks me something, I will say yes if I know it, and if I don’t know it, I won’t. I won’t pretend to understand, nor will I pretend to understand. Don’t have too much hope.”

During breakfast, Qiao Xi vaccinated Qiao Yu.

These words made Qiao Yu, who was originally confident, feel a little uneasy.

Qiao Xi felt that Qiao Yu was a little bored, and he wanted to alarm the academician with such a big deal.

Qiao Yu really wanted Qiao Xi to be valued by Mr. Yuan and come to the capital in the future. Not only would he be closer to Qiao Xi, but the key was that he could discuss mathematics with Qiao Xi and then despise her.

Anyway, no matter how strong Qiao Xi is, she can't be stronger than him.

"I know! We are all wild people anyway, but I still think that people who can casually read Schulz's papers must be talented."

Qiao Yu ate his porridge and steamed buns with his head down, and was too lazy to argue with Qiao Xi anymore. Anyway, he would know it when he got to Huaqing.

The two sides were very close to each other, and they were not in a hurry. Qiao Yu didn't use the number given to him by Director Tian and took Qiao Xi directly to Qiuzhai in Huaqing.

In fact, except for the road section, the scenery on both sides of the campus is pretty good, especially the road from Huaqing to Qiuzhai.

But the most important thing is that even though it is already July, the mornings in Star City can already make people sweat on their foreheads. The temperature in the capital is only around 20 degrees, making it very comfortable to walk on the road.

Twenty minutes later, Qiao Yu led Qiao Xi into Mr. Yuan's office.

To his surprise, Professor Tan was also there.

After the greetings, the four of them sat on the sofa where the old man was entertaining guests, and each had a cup of still-smoking hot tea in front of them.

Qiao Xi also immediately sincerely apologized to the old man on behalf of Qiao Yu: "Mr. Yuan, Qiao Yu was really reckless yesterday. In fact, I can only say that I am interested in mathematics at best.

I really don’t think I have much talent. More than ten years ago, when I was in high school, I didn’t show much ability in mathematics. It was even difficult for me to get full marks on the high school test paper.”

Mr. Yuan smiled and shook his head and said: "Don't talk about it, whether you have mathematical talent or not is a trivial matter. But the idea you proposed yesterday, Lu Yuan and I both find it very interesting. I just invite you to have a casual chat today.

"

This sentence also made Qiao Xi feel relieved and she became more relaxed.

The mother is still afraid that because of her, the boss will be more harsh on Qiao Yu.

So the four of them chatted about something, and then the old man praised Qiao Yu in a fancy way, and then slowly turned to the topic of mathematics.

"By the way, Qiao Xi, I heard Qiao Yu say yesterday that you could independently understand Schulz's paper?"

Professor Tan asked casually.

Qiao Xi thought for a while and replied pertinently: "Part of it. I can't say I fully understand it."

"Do you have any foundation in advanced mathematics?" Professor Tan asked.

"I occasionally looked through the mathematics books that Qiao Yu borrowed before, such as linear algebra, calculus and mathematical analysis. I have read more documents during this time."

Qiao Xi answered casually.

"Oh, if you were asked to choose between linear algebra and calculus, which one do you think is more interesting? Which one do you think it would be, relatively speaking?"

"That should be linear algebra."

Qiao Xi thought for a while and said.

Professor Tan smiled, then looked at Mr. Yuan, thought for a while, and said: "There is such a sequence, the first three numbers are 1, 3, 7... Do you think according to this rule, the fourth number should What is it?"

When Professor Tan started to ask questions, Qiao Xi was not doing well yet, but Qiao Yu sat upright first.

"23." Qiao Xi gave an answer casually.

Tan Luyuan nodded and asked with a smile: "Think about it again, if there is a 3X3 square grid, the starting point is in the upper left corner and the end point is in the lower right corner.

The rule is that you can only move right or down, don't draw a picture, and your first impression is that there are several different paths to get from the starting point to the ending point."

"Six kinds." Qiao Xi smiled and replied.

Tan Luyuan nodded, and then found that Qiao Yu seemed to glare at him secretly...

I was a little stunned at first, but I figured it out instantly. Maybe I thought the question he asked was too simple?

But he ignored it, just smiled and asked: "Qiao Xi, have you ever studied graph theory?"

Qiao Xi shook her head and said softly: "No, I have never been in contact with him."

Tan Luyuan smiled and said: "It's okay, let me explain two concepts to you. There is a basic structure in graph theory called an undirected graph, which is composed of vertices and edges. The edges represent the connection relationship between the vertices. The characteristic is that the edges have no direction.

For example, if there is an edge u, v, then it can be connected from u to v, or from v to u, and the relationship between the two is equivalent.

A loop refers to a path that starts from a certain vertex, passes through a series of edges and vertices, and finally returns to the starting point. Note that in a loop, the vertices in the path other than the starting point and the end point cannot be repeated. Can you understand these two concepts? ?」

Qiao Xi nodded, as if this was indeed nothing unusual for her.

"So now there is an undirected graph, the nodes are A, B, C, D. The edges are A-B, B-C, C-D, D-A, A-C. So do you think there is a cycle in this undirected graph? If so, do you How many rings do you think there are?”

Tan Luyuan asked again.

Qiao Yu raised his head and looked at the ceiling. He even thought that Tan Luyuan was trying to test his mental retardation.

Fortunately, Qiao Xi did not hesitate at all and answered: "There should be two, namely ABCA and ACDA."

"Well, that's right, that's right. Why don't I ask a question too? You can answer whatever you like."

Yuan Zhengxin, who had been listening quietly next to him, seemed to suddenly become interested and took the initiative to interject: "In this way, consider an irregular decahedron, and each face is an irregular triangle.

It is known that this decahedron has only seven vertices. The question is how many edges this decahedron has, and if possible, summarize the adjacent relationship of each face."

This time Qiao Xi thought for a while before answering: "There should be fifteen sides? In terms of adjacent relationships, because each face is a triangular decahedron, each face should be related to the other three faces. Adjacency relationship."

Well, Qiao Yu found that he was confused because he was concerned.

Mr. Yuan probably made the arrangements with Professor Tan.

Although these questions are simple, the test items are not complicated, and they do not even involve very advanced mathematical knowledge.

But the things tested are actually the same. They are all about abstract thinking and spatial imagination.

It seems pretty good to be able to come up with these questions in a short period of time.

Qiao Xi really didn't disappoint him. The answers were all right. At least they were right in his opinion.

Sure enough, he was still a little naive. Although he thought Qiao Xi must be talented in mathematics, he didn't expect that she could be tested in such a simple way.

"Qiao Xi, your situation is very interesting. I guess you will never get lost."

After listening to Qiao Xi's answer, Mr. Yuan also smiled and gave an evaluation.

Qiao Xi nodded, she agreed with this point.

"Well, in our family, only Qiao Yu's grandmother is blind and can't always tell the direction. Everyone else has a good sense of direction. As long as they have been to a place once, they can definitely find the way."

Mr. Yuan smiled and analyzed seriously: "Yes, you and Qiao Yu both have strong spatial imagination. This is indeed a rare talent. With strong spatial imagination and exposure to abstract algebra and geometry, you will often get twice the result with half the effort.

Especially when you are exposed to high-dimensional concepts such as gradient, divergence and curl, and when you need to perform optimization analysis, this ability can help you quickly understand the essence of the problem.

This is also the reason why you are more interested in linear algebra. The introductory content of linear algebra is actually more abstract than the introductory content of calculus.

But if you come into contact with multivariate calculus, you will find that these knowledge are actually very interesting and closely related. So there is no need to doubt yourself because you can't get full marks on high school questions.

After all, the exam focus at different stages is different, and high school focuses more on specific application orientation. For example, I guess you will be able to learn functions, geometry, and sequence in high school with ease.

At the same time, you will definitely get tired of questions that require a lot of calculations. I think this is why it is difficult for you to get full marks on high school questions."

Qiao Xi frowned slightly and started thinking about what happened in high school, it was a bit long ago...

Qiao Yu kicked Qiao Xi without leaving any trace.

The two of them are really too familiar.

Qiao Yu knew that once Qiao Xi showed this expression, it wouldn't take long before her attention would begin to wander, and her mind would wander.

This state usually lasts for several minutes when no one reminds me or there is no alarm clock...

Qiao Xi looked at Qiao Yu, then looked at Mr. Yuan who was still smiling, smiled apologetically, and replied: "Well, maybe. I actually don't pay much attention to these."

"It's not possible, it's definitely the case. It's like you can understand Schulz's paper."

After speaking with certainty, Yuan Zhengxin paused and asked: "Since you know Schulz's paper, you should know the concepts of metric space, density, completeness, and Cauchy numbers, right?"

Qiao Xi nodded and said, "I didn't understand it at first. But if there were concepts I didn't understand, I would look them up, and I gradually understood them."

"That's fine. I'll ask a question. You don't need to prove it. You just need to use your first impression to answer my proposition. Do you think it is correct or wrong?"

Mr. Yuan continued.

Qiao Xi nodded slightly again.

"Suppose (X, d) is a metric space, and YX is a dense subset. Now assume that Y is a complete space, then X is also a complete space. Do you think this proposition is correct?"

Qiao Xi thought for two seconds, then shook her head slightly and replied, "I feel wrong."
To be continued...