Xueba, I beg you to go and escort him quickly!

Xu Heng slowly opened his eyes, glanced at Yue Pingting, and then glanced at the title on the phone.

"Ha... this question uses the Fibonacci sequence."

Yue Pingting thumped, looked at Xu Heng, "Are you awake?"

Xu Heng yawned.

"Why, do you have time to delve into this kind of topic?"

Yue Pingting stuck out her tongue, "It's kind of boring."

Xu Heng smiled, "Since it's boring, let me teach you something else!"

Yue Pingting, "???"

Xu Heng, "Let me teach you something new in mathematics!"

"However, if you want to learn this thing from the beginning, the first thing to learn is the most difficult one, and it is usually the finale."

Yue Pingting frowned, "???"

"What the hell, what did you learn first, but it became the finale?"

"Xu Heng, are you sure you didn't make a mistake?"

Xu Heng explained, "I want to teach you calculus, but I must first learn from the limit."

"You can look up the history of the development of calculus on the Internet, there is information."

"I won't say much here. I mainly say that the limit is finally established by the whole calculus."

"Do you know why?"

Yue Pingting, "???"

Xu Heng, "It's just that Newton Leibniz didn't understand this chapter at all. Because of the 200-year development history, five generations of people are the founders of the fifth generation of calculus, and only established the system and definition of the limit."

"Cochy is finished!"

"The definition given by Wilstras."

"The content of the limit was developed in the last few decades of the entire 200 years, but this is what everyone studied all the calculus problems, and finally found that there is no definition of the limit."

"It's just that no one has done the most basic things, so someone came up with it later, and this discipline is complete."

"But when writing the book, I put the things from the last few decades into Chapter 1, because it is the foundation of the entire discipline."

Yue Pingting was confused, but fortunately, what Xu Heng taught next had something to do with what he just said, but it was just a concept and understanding relationship.

Yue Pingting took a deep breath and frowned.

She looked at Xu Heng seriously.

And Xu Heng also saw from her sincere eyes that it was time to teach Yue Pingting the content of the university.

Because of high school, she had already learned everything in the last semester!

After this semester, she continued to consolidate and consolidate again!

Moreover, she has already proved her strength with the monthly exam!

Under such circumstances, Xu Heng knew that Yue Pingting was getting bored!

She is getting bored!

Just like during the winter vacation, Xu Heng asked Xu Zongyun to play games all the time.

This requires an increase in desire!

The more eager you are, the more focused you will be.

So Xu Heng knew that Yue Pingting was coming to a spiritual world point soon!

"Come on, let's see..."

Xu Heng picked up the pen and paper, and slowly explained to Yue Pingting.

And what he said was different from the way those teachers taught in the university classroom. Xu Heng used the topic as the starting point!

From point to line!

From line to surface!

In this way, she can help Yue Pingting learn more deeply.

Although she has also been exposed to limits, calculus, and derivation before, the real university courses are much more difficult than those learned in high school!

or!

Some teachings and concepts in high school are one-sided from the perspective of universities!Not rigorous!

Yue Pingting had a hard time studying at first!

After all, this is a university course, and Xu Heng didn't play his cards according to common sense.

Anyway, Yang Kaixuan couldn't understand it at all!

After repeating this for two weeks, Yue Pingting felt much easier.

And Xu Heng is also preparing to go to the Eighteen Provinces Mathematical Olympiad to qualify for the paper group!

The person who came to pick him up was the same driver as before.

Several times in a row, although there was not much conversation between the two, Xu Heng was inexplicably relieved when he saw him.

The two smiled at each other.

After getting in the car, Xu Heng didn't ask where he was going.

He didn't care about anything.

He just checked in the car, and there was paper and pen in the back, and there were chargers and power banks beside him, and everything was well prepared.

Xu Heng smiled.

He is really a person who does the details in place!

The last one who was so in place was Han Honghu.

Xu Heng took a deep breath and took a comfortable nap.

When he woke up again, they were still on the highway.

Xu Heng was bored.

After scrolling through the group news, he waited for a topic to catch his eyes.

After probably looking at the group photo album, there was indeed a question, which aroused Xu Heng's interest.

topic:

As shown in the figure, the trolley with mass M=kg is still on a smooth horizontal surface, the AD part is a rough horizontal guide rail, and the DC part is smooth

1/4圆弧导轨，整个导轨由绝缘材料做成并处于B=1.0T的垂直纸面向里的匀强磁场中，今有一质量为m=1.0kg的金属块（可视为质点）带电量q=2.0×10-3C的负电，它以v0=8m/s的速度冲上小车，当它将要过D点时，它对水平导轨的压力为9.81N(g取9.8m/s2)求：

(1) When m goes from A to D, how much mechanical energy is lost by the system?

(2) If the magnetic field is removed immediately when m passes through point D, what is the maximum speed obtained by the car after that?

Xu Heng set a time for himself.

He didn't use a pen or paper, but just calculated the answer in his head.

1 seconds... 2 seconds... 3 seconds... 4 seconds...

Xu Heng murmured, "." The lost mechanical energy is 18J, and the maximum speed gained by the car is... 3 seconds per meter..."

After giving the answer, Xu Heng looked at the time.

30 seconds!

After reading the question, Xu Heng gave the answer to this question within 30 seconds.

From the very beginning, Xu Heng's so-called interest was to challenge his own limit time, not to find this question attractive!

That's it!

Xu Heng repeatedly scrolled through the topics in the group photo album.

A question!

Another question!

There are about 300 questions!

But there are only 50 questions that can measure your eyes in this way!

But for these 50 questions, it took Xu Heng less than two hours from reading the questions to giving the answers to these questions!

When Xu Heng finished the last question, Xu Heng suddenly felt unfinished.

In the group, Xu Heng @集主.

"@集主, are there any other topics that haven't been uploaded?"

Lord,"???"

"Master Xu Heng, what do you mean?"

Xu Heng, "Take the car. I'm bored in the car. I finished all the questions in the group photo album. I just want to ask you, do you have any other questions?"

At this moment.

The people in the group who watched Xu Heng's words were all stunned, staring at their mobile phone screens or computer screens.

They can't wait to put their eyes into the screen and read Xu Heng's words word by word, stroke by stroke.

!!!

Nima!

I'm bored and finished all the questions!

Come on! ! !

Someone stood up and asked directly, "Master Xu Heng, did you take the train for a day and a night?"

"???"

"Isn't it more than a day and a night?"

Xu Heng, "Eh...not long, not long! Don't change the subject, I'll ask the group leader!"

"(得李好)@集主! What topic are you still hiding? Take it out!"

Xu Heng has always felt that with so many people, it is impossible to only have these 300 questions!

At this time, the group leader chatted privately with Xu Heng!

Voice private chat!

"Big Brother Xu Heng! You, you... hiss! Are you sure you've finished reading it all? How long did it take you?!"

"These questions are all kinds! Mathematics! Physics! Chemistry! And there is no distinction between high school, university, and graduate students, regardless of the type of questions. It's too mixed! Have you solved them all?"

"???"

"It's only less than 12 o'clock now! Even if you took the bus from 6 o'clock...you, it's only been more than five hours!"

"hiss……!"

"And this is the one I counted more! You can't sit on the train all night and master the questions for 12 hours, right?"

"Impossible... We know some questions, and you know the answer by doing the math?"

"Brother Xu Heng, this is a relatively difficult, or difficult, very dark topic that we have collected since we established the group last year!"

"As far as the questions that appear in this question bank are put outside, let alone students, even teachers, even university professors, will feel uncomfortable and quit!"

Xu Heng, "Go, go, go! Don't tell me these things are useless! I'm just bored, and I'll disappear after I'm done. Do you have any new questions? Upload some."

Group leader, "Puff——"

He worked hard and finally selected the topic!

"Master Xu Heng, you...you...!!!"

"Hey... these 300 questions, but we have carefully selected them for a long time!"