"Be a man to be open-minded, if you're late, you'll be late, can't you walk in through the front door openly?"

Gan!

It's not like I'm afraid of disturbing your class.

Isn't it an international practice for those who are late to enter through the back door?

A pair of eyes looked over, even though his face was still relatively thick, Hao Yun was a little embarrassed.

Just when he was hesitating whether to go through the front door again, Li Xuesong on the stage coughed and continued with a straight face.

"Where's the homework?"

Job, homework?

Hearing this, Hao Yun's face suddenly became embarrassed.

"Uh, I forgot to bring it."

Forgot to bring?

Hehe!

If you don't write it, you don't write it, and you still find this kind of low-level excuse.

Looking at Hao Yun with a smile, Li Xuesong continued with a smile: "Forgot to bring it? Okay, you mean it's written? Anyway, it's just one question, so it's okay for you to write now, right? ”

As he spoke, he tapped his index finger on the blackboard.

"Come here and write."

Hearing the old professor's words, there was a commotion in the class, and many people turned their heads and ears.

Hao Yun, who was standing in the back row, couldn't hear what they were talking about, and just wanted to complain that the old professor didn't know what kind of nerves he had today. I didn't do anything hurtful, but I was a minute or two late, so it's so difficult.

Looking at Lao Li's smiling expression, he knew that he was destined to be doomed today.

In his heart, he scolded the second goods who followed his draft book, Hao Yun sighed, and finally walked towards the podium.

When passing by the front row, he noticed that Zheng Xueqian was frantically throwing his eyes and handing over the words, and poked the screen of his mobile phone vigorously, as if to signal him to look at WeChat.

[Are you crazy?! Is it really up? No one wrote that question! 】

Although I can guess that this good brother probably sent him the answer to his homework, he has already come here, and he obviously has no chance to take out his mobile phone.

Hao Yun gave him a reassuring look and made eye contact.

[Don't worry, I'm fine.] 】

Facing the "confident" eyes, Zheng Xueqian was blindfolded for a moment.

it?

What does this guy mean?

Won't it ...... It's really written, right?

Impossible!

He Shen didn't even write the question......

The touch of his eyes was only a moment's work, and before he could confirm whether he was wrong, Zheng Xueqian watched Hao Yun stand on the podium.

Taking the chalk from Lao Li's hand, Hao Yun stood in front of the blackboard for a while, and suddenly turned his head a little embarrassed.

"Uh, what's the title...... I didn't memorize it. ”

As soon as he heard this, Li Xuesong immediately smiled, and said in his heart to see when you act, and pointed to the podium with his chin.

"There are so many on the lectern, you can copy a copy of it."

It's okay to copy a copy......

Aren't you afraid that I'll see the answer?

Hao Yun, who casually picked up the top homework, muttered a few words in his heart, but within a second of opening it, the whole person was stunned for a moment.

Good guy, just write a "solution".

Isn't this going to be a regular share?

Hide the book downward!

Looking at the name again, it is still Liang Ziyuan's.

Silently wrote down the topic, and Hao Yun helped him stuff the homework book to the bottom very righteously.

Taking in the small movements of this student, Li Xuesong smiled and did not debunk it, but just raised his eyebrows and continued.

"Do you know the title now?"

"Uh, I remember."

"Remember? Okay, then stop talking nonsense, let's get started! ”

Originally, it was not a particularly difficult question, and even the letters that appeared were only a few, and all the information about the question stem could be explained clearly in two sentences.

Hao Yun didn't think much about it, turned around and copied the question on the blackboard, and then read the question carefully from beginning to end again.

However, it doesn't matter if you copy it.

When he finished copying the question and read it again, the whole person was stunned.

[Let the positive integer a, b satisfy (a²+b²)/(ab+1)=k∈N, and prove that k is the square of a positive integer.] 】

Boy.

This question......

Familiar, huh?

Seeing that Hao Yun didn't move for a long time, Li Xuesong thought that he wouldn't, so he smiled and joked: "If you can write it, you won't have to take my class in the future, and all the credits will be given to you." ”

Hao Yun swallowed his saliva, and asked in disbelief.

“…… It's true? ”

"Heh, I need to lie to you?"

Then I really wrote it......

Confirming that this guy didn't seem to be talking back, Hao Yun hesitated for a moment, and finally pasted the chalk on the blackboard and began to move the pen.

[Let k not be the square of a positive integer, then there is a≠b.] 】

[Considering the indefinite equation a²-kab+(b²-k)=0, if a=b, k=1 can be deduced, so it contradicts the hypothesis.] 】

[Therefore, you may wish to set a〉b〉0 and take a set of solutions (a0, b0) so that a0+b0 is the minimum ......]

Although he copied this question in the draft book before, Hao Yun never took the time to read it carefully, otherwise he would not be surprised here.

And the reason for the surprise is simple.

Because this is not only the original question, but also the sixth question on the earth in the previous life, the 1988 IMO International Mathematics Competition!

As for why he would know......

It's not because he participated in that competition, but because just yesterday, he saw it in that notebook-filled high math textbook, and finally did it himself.

He even remembered that the question had been copied in the blank space at the end of the page on Vedic Theorem.

According to Professor Lu's slightly ridiculous comments, no one from the main examination committee made this seemingly simple number theory question back then, and finally asked for help from 4 number theory experts in Australia, the host of the competition, for a while.

Since the experts could not solve this problem within the allotted time, this problem has become a legend.

Out of a total of hundreds of contestants, only a dozen contestants wrote their answers, and one of them even received a special prize from the main examination committee of the competition for his beautiful answers.

At this moment, the solution he was writing on the blackboard was the "standard answer" that was awarded the special prize that year.

What is very interesting is that, according to Professor Lu's writing, these dozen contestants who wrote the answers eventually became famous figures in the field of mathematics. And when commenting on this little-known past, the professor also wrote with emotion-

[Normally, mathematics is a product of intuition, but some counter-intuitive propositions are not excluded.] Just as our common sense always tells us that counter-evidence is unreliable, our common sense occasionally deceives us against common sense. 】

[It's just that I'm a little surprised, even Tao Zhexuan, who shouldn't have lost to this question, was unfortunately planted in its hands. 】

Although he had no particular interest in mathematics, and Hao Yun had never heard of the names mentioned by the professor, he still drew a solid conclusion from the limited amount of commentary.

This notebook is probably a relic of some famous person in a past life - or even a great person?

Thinking about it like this, I suddenly felt like a holy relic.

The only pity is that when he finished reading the notebook, the system didn't even give him a trace of dust, and directly erased the existence of that thing from this world.

Just when Hao Yun was thinking nonsense and writing the answers on the blackboard according to the ideas of solving the problem in his impression, Professor Li Xuesong, who was standing next to him, looked stupid.

If it's a scribble, it's fine, at most, after this guy finishes writing, he will laugh at it next to him...... Oh no, criticize education two sentences.

But this guy wrote it, and he couldn't find anything wrong with it!

I even feel ......

Seems to make some sense?!

Especially when Hao Yun wrote the fourth line, his whole face changed.

it!?

This problem can be solved like this?

He was not the only one who was shocked, but also He Ping who was standing in the audience.

Staring intently at the blackboard, he couldn't help but whisper in his mouth.

"Counter-evidence? It's actually a counter-evidence?! No way, I've tried to disprove it before—"

"I see...... I get it...... I see......"

Zhou Xuan and Wang Ziyi, who were sitting next to him, looked at each other and exchanged a confused gaze.

Zheng Xueqian, who was sitting in the back row, swallowed his saliva, and his nervous pen was about to crush.

It's not that I'm cheering for Hao Yun, but I didn't expect this guy who sleeps diagonally opposite him to be so awesome!

Careless......

Zhu Kening and Liang Ziyuan didn't have any special reactions, one was not interested at all, and the other couldn't understand it, but they just felt a little awesome.

The entire 1801 and 1802 classes were silent.

Whether it is a real scholar or a fake scumbag, looking at the process of writing on the blackboard, almost everyone is stunned.

He didn't pay attention to the expressions on the faces of the people behind him, and Hao Yun was completely focused on the blackboard, feeling that he was entering an unprecedented state.

How so?

It's as if the whole world has slowed down.

Only his mind continued to accelerate......

Is it because of [math mastery]?

It turns out that this is the effect of quantitative change causing qualitative change......

Although his intuition told him that the accelerated mind could be faster and could be further developed until he finally touched the so-called realm of God! But for him at this moment, even this level of acceleration is completely sufficient.

What is in front of me is just a topic that has been written, and it is far from being a creation.

A glimmer of realization gradually rose in my heart.

Until this moment, Hao Yun finally understood a little bit of what kind of existence this so-called system of outsiders was.

The hour hand on the wall walked second by second.

After almost three turns, he stopped the chalk in his hand and turned his head to look at Lao Li who was standing next to him.

“…… I'm done. ”

I don't know if I didn't hear what I said, Professor Li Xuesong didn't react, and he didn't even move his eyebrows.

In order to confirm that the old man was not asleep, Hao Yun asked politely.

"Is there anything wrong with the steps?"

Hearing this inquiry, Professor Li Xuesong finally came back to his senses.

I saw him staring at Hao Yun with both eyes, then at the blackboard, and then moving his stiff neck as if shaking his head and nodding his head, and spit out a sentence from his mouth.

"No problem......

Hearing this, the stone hanging in Hao Yun's heart finally fell to the ground.

It is worthy of Jiang University.

It's true, some!

In the previous life, I had to put aside the exam questions that added to the IMO competition, but in this life, I was only worthy of thinking after class for the first lesson of high mathematics.

A pressure arose, and Hao Yun was embarrassed to ask the professor if he really didn't use it in the future, and after saying "Then I'll go down", he quietly slipped off the podium.

The whole classroom was silent.

I don't know who started it, but it applauded.

He Ping sat back with straight eyes, not knowing what he was muttering.

When he returned to the last row and sat down, Hao Yun always felt that there seemed to be a lot of people watching him around him, which also made him, who had always had a low sense of existence, feel uncomfortable for a while.

Fortunately, the applause only lasted for a short time.

As Professor Li Xuesong returned to the podium without saying a word, the students in the classroom also re-entered the state, staring at the blackboard carefully and preparing to listen.

The answer is the same as what this classmate wrote, which is basically a standard answer...... You copy it, take a photo if you don't have time to copy it, and ask him if you don't know, I won't talk about the specific details. ”

"Turning to page 12, we continue with the ...... from the previous lesson"

I don't know if it was stimulated by something, but Professor Li Xuesong in the second half of the class uncharacteristically did not repeatedly nag those difficult words such as "young people now" and "how are the men of our old calendar" in class.

It's just that I don't know if it's my own delusion, Hao Yun always feels that he is a little absent-minded standing on the podium?

Or rather, the soul is not kept.

Thinking of this, Hao Yun couldn't help but be a little worried, did his late behavior make him angry?

But shouldn't it?

People are not saints and sages, not to mention that they are just late, they should admit their mistakes and have a correct attitude! If you can still be angry, then you are too careful, right?

and Zheng Xueqian......

This guy kept looking back at himself in class, which made Hao Yunwei embarrassed.

The bell rang between classes.

Professor Li Xuesong dropped the high math book without saying a word and left.

Everyone thought that he was going to solve the internal emergency, but they didn't expect that five minutes later, after the class bell rang, it was a doctoral student who came.

Looking at the hairstyle that has been passed down from generation to generation, it is his students who can't make a mistake.

Sure enough, his opening remarks also confirmed the conjectures of the big guys.

"Professor Li Xuesong has some things, and I will teach you the second half of the class."

Looking at the little newcomers in the classroom and smiling, the doctor picked up the textbook on the table and scratched the back of his head.

"Well, the professor left in a bit of a hurry just now......"

"Can anyone get up and tell me where he just went?"