Chapter 14: Lagrange's mean value theorem

Police station, communication room.
The policeman and Song Yu had big eyes to small eyes.
The policeman held a pen and smiled, "Why are you again."
Song Yu replied slowly: "Probably because I am born with a strong sense of responsibility, I like to call the police when I encounter unfair things."
The police were amused: "No, what I asked was, you are always the one who was beaten by the gang."
Song Yu: "......"
Xie Sui laughed aloud next to him.
The gangsters actually suffered more injuries than them, but the group of Hong Mao had been recorded in the police station and had countless criminal records. The police considered them a legitimate defense, and just took a brief record and let them go. Originally, he wanted to contact his parents. Song Yu took the initiative to talk about the situation in Xie Sui's family, and his words were emotional and reasonable, and this link was cancelled.
It's the same police station again, and it's the same small clinic.
There are several people in the clinic with bright lights.
The male doctors in the clinic still have an impression of them.
Doctor: "Last time it was a leg injury. This time it was a hand injury. I used a real knife to do it. Young man, you are pretty wild."
Xie Sui sat on the chair with his eyes slightly bent, smiling modestly and saying, "It's okay."
The doctor was so angry that the pen stroke almost broke on the paper: "I said you are still proud of you? You are prestigious outside. Have you ever thought about how the family is worried? Just study me in peace, and you have to follow the group of social youths who are not doing their jobs properly. If something goes wrong, it is your parents who are sad."
Song Yu held his mint candy and spoke to Xie Sui: "Uncle, you have misunderstood. You can't just look at the surface."
The doctor gave him a blank look: "I haven't trained you yet. Your kid is his friend, right? So you just watch him fighting there? Don't persuade you?"
Song Yu choked, his face a little embarrassed, and scratched his head: "We are not talking about the same thing."
The doctor put the medicine into the bag and sneered: "Yes. Then, regardless of the surface, are you going to fight against the scars left by the aliens? The aliens also use such down-to-earth cold weapons?"
Song Yu: "......"
Tiga Ultraman is on the TV hanging on the wall. The doctor's two-year-old son listened, clapped his hands and turned his head, his clear eyes curled up, and his milk laughed: "Crooked Xingyin."
Xie Sui paid the money and took the medicine, "Thank you."
The doctor hates iron but steel: "My son will grow up in the future. If he hurts himself like you all day long, I will break his leg first."
Song Yu chewed on the candy and yelled: "I said that I can't look at the surface, what's wrong with you, uncle. My friend is Chuan Anliang who was injured. He just fought against the street fighter with one enemy and one hundred. He defended all the north, south and north of Lianyun Street. The personal safety and property safety of junior high school students. These injuries are the scars of heroes."
Doctors:"......."
The child sitting in the chair drooled and clapped his hands: "Hero."
Song Yule said, "Eh, the kid is so smart, say it again."
The kid who was praised had a very sweet smile, milky and milky: "Brother, hero."
The doctor saw that he was still teaching his children bad, and he was so angry that he took a feather duster to drive them away: "Walk around and fight the street fighter bravely. I think you are the biggest bully on Lianyun Street."
"Puff hahaha."
Song Yu, who was promoted to Street Fighter, couldn't laugh, and pulled Xie Sui out.
A few moths gathered on a street lamp outside the clinic. On a quiet summer night, the moan of small insects came from the bushes.
It was very late now, Song Yu stood under the street lamp, called Uncle Ma, and asked him to pick him up at the old place.
After hanging up the phone, Song Yu turned to Xie Sui and said, "I won't come here much in the future. See you at the beginning of summer vacation."
Those gangsters have a criminal record, and this time it is estimated that they will have to stay in the game for several days. Xie Sui should be safe in July and August.
Solved the most dangerous thing he would encounter in summer vacation.
Song Yu felt that there was no need to go here anymore.
Xie Sui's breath still smelled of mint.
Can't help but wonder how Song Yu likes mint.
He closed his fingers and smiled: "Well, see you at school."
Song Yu stared at him, thinking of the fiercely fighting teenager in the deep alley, speechless for a while.
He felt that he didn't understand Xie Sui for a moment, but it seemed that he had never really understood.
Get in the car, leave the remote residential area, and walk towards the bustling city center.
The neon lights shined on Song Yu's thoughtful face.
Uncle Ma asked: "Master still came to your friend who hit it off?"
Song Yu returned to his senses: "Yes."
Uncle Ma said: "You run around every day, the old lady is suspicious. I think you come a few more times, she will see your classmate."
Song Yu laughed: "It's not coming, it's not coming."
In fact, it's okay to let Grandma Meng see Xie Sui.
It's just that he promised that 008 would not appear next to Xie Sui as the third young master of the Song family. In the future, he plans to make up an identity as a "poor relative of the Meng family".
There are very few people in Song Yu’s QQ add. He was lying on the bed and playing with his mobile phone. Looking at the dark head of Jun Hao Jun, his hands were a little itchy and he wanted to send something.
But today I was racking my brains for bad reviews, and ran a street again in the middle of the night. I'm exhausted and tired.
I didn't know when I fell asleep.
When I got up the next day, it was already nine o'clock in the morning.
Going downstairs for breakfast, Song Yu was bombarded by Ma Xiaoding.
[Sadako does not forget the man who digs the well: puff ha ha ha ha ha ha ha ha ha ha]
[Sadako does not forget the man who digs the well: Is it you that brother Yu is crazy to criticize? I went to him to eat on purpose today. Seeing Zhu Zhixing's mother's face turned blue, I guess I was going to die of anger. 】
[Sadako does not forget the well digger: Puff ha ha ha ha, so talented, I also asked my little brothers to follow your steps, and went to brush a few. Angry at this vicious woman! 】
Song Yu was already too lazy to care about Zhu Zhixing's affairs. Thinking of Grandma Meng's expectant eyes and the stack of papers on the table, he suddenly had a headache.
He drank milk mouthfuls and sent messages to Ma Xiaoding.
[Your husband Yu: How are your grades? 】
[Sadako does not forget the well digger:? ? ? 】
[Sadako does not forget the well-digger: I asked about this, it's okay...Is it. 】
Can be admitted to Jingcheng No. 1 High School, the grades are not considered bad.
Song Yu curled his lower lip and started typing.
[Your husband Yu: Good grades in junior high school may not necessarily be good in high school. Don’t think that you can relax this summer vacation after the high school entrance examination. Others are now crazy to apply for cram school. One China is under great competition pressure, and there are jumping off buildings every year. It is luck not to be blocked by the government. High one can't lose at the starting line. 】
Ma Xiaoding was shocked by his speech like his dad.
[Sadako does not forget the well digger:... Brother Yu, what are you trying to say? 】
Song Yu had already returned to the room, pulled out the chair, and sat down at the table, looking at the mountains of papers.
[Your husband Yu: Come to me, I will share some knowledge for you. Good brother, make papers together. 】
[Sadako does not forget the well digger:...]
This good brother can't do it right.
By dividing the paper into half of Ma Xiaoding, Song Yu felt a lot more comfortable.
Grandma Meng gave him a lot of information, and during the transitional period, many of them were used to consolidate and review junior high school, and then infiltrate high school knowledge bit by bit. There are even the original questions for the college entrance examination, just to give him a good idea of ​​the difficulty.
Except for the first paper, Song Yu didn't even prepare to write on his head, and slowly found a little feeling later.
I just pulled a piece of paper at the bottom of the booklet, it was very difficult and it was not required to do it. Song Yuxian turned to the last question without problems, and was stunned.
A very classic function problem, e to the power of x and e times x.
He hasn't planned to try the finale yet, but vaguely feels familiar, and even a very vague concept appeared in his head. Biting the pen for a long time, I finally remembered.
This is not a typical example of Lagrange's median theorem!
He will remember this question still fresh, and it is probably because the name of the theorem that the high school teacher referred to when he expanded his idea of ​​solving the problem is too weird.
The theorems given on Baidu, without combining specific examples, are very puzzling. Song Yu just wanted to finish the first conversation with Xie Sui.
So I took a picture of this question and sent him a message.
For the shame of Yi Xue's a66, he bit his pen and thought about it.
Pretending to be profound.
[Do you know what is Lagrange's median theorem? 】
Xie Sui was leaning on the bed, tapping his fingers on the computer, invading the Linshui Intranet and calling up the monitoring records.
After everything was done, I grabbed the water glass next to me and caught a glimpse of the message on the phone.
[Song Yu: Do you know what is Lagrange's median theorem? 】
Xie Sui: "......"
He should be thankful for not drinking water.
Xie Sui's academic performance has always been outstanding during his student days, and his personality is withdrawn and cold, and he has never met any normal classmates.
Therefore, it is not possible to understand Song Yu's brain circuit, which relies on perseverance in solving problems.
You have to count permutations and combinations. Why do you ask Lagrange?
Of course, Xie Sui didn't talk about this self-esteem problem. Because he could see that Song Yu seemed to have a high enthusiasm for learning, and he didn't want to hit him.
Xie Sui took out a pen and a piece of paper, taking care of Song Yu's knowledge reserve, wrote down the standard solution of the question in detail, and then took photos and sent them.
【Xie Sui: [图]】
[Xie Sui: No need for that. 】
Song Yu waited for a long time, then waited until he said something like this, accompanied by a photo with clear thinking and beautiful handwriting.
It is even easier to understand than the answer.
Niubi is worthy of being the protagonist and the proud son of heaven.
But when Song Yu got to the tip of a horn, he would persevere and continue to ask.
[Song Yu: How do you use that solution? 】
A few emoticons were sent by the way.
【[Scratch head question mark]】
【[Ballballyou]】
Xie Sui's finger rested on the little soybean scratching his head, as if seeing the troubled look on Song Yu's phone, his expression was a little surprised, and then his lips twitched.
[Xie Sui: So you want to know? 】
[Song Yu: Right. 】
[Xie Sui: Cross out the large section from the third row to the fifth row and turn it into "Knowable from Lagrange's median value theorem". 】
"???"
After Song Yu did what he said, he sighed with scumbag.
[Song Yu: So there is a number in the interval to make them equal. 】
Xie Sui didn't want to tell him that it was a theorem. After thinking about it, his eyelashes drooped and his dark pupils smiled with a little wicked taste.
[Xie Sui: Didn’t I give you a range? You can substitute one by one, you can always find that number]
Song Yu: "......"
Song Yu: "..............."
Your mother's range is unlimited!
Why does he always feel that Xie Sui is laughing at him.