My Identity As A Schoolmaster Has Been Exposed

Xu Cong is naturally not a stingy person. The classmate was just talking. After he finished washing, he went to bed and continued to play with his mobile phone.

When Yang Kaixuan saw Xu Cong's calm look, he also sighed and corrected the roommate's words.

He retorted: "I am me, Xu Cong is Xu Cong! I can't do it! You can only use Xu Cong's words."

"Do you think Xu Cong said that these questions are too simple. They are joking, pretending to be thirteen?"

When the people in the dormitory heard Yang Kaixuan's seriousness, they looked at each other and felt that he was praising Xu Cong.

So they also whispered to Yang Kaixuan: "Yang Kaixuan, you are too humble!"

Yang Kaixuan was stunned, with a strange expression on his face, and then he said to several people again: "You actually think I am humble? What I said is the truth! I really don't know these questions! I have to ask Xu Cong, please!"

After that, Yang Kaixuan got up and spoke to them very seriously: "If the college entrance examination questions are to get most of the candidates to score, but they can’t get high scores, then the Mathematical Olympiad questions are for most of the candidates. I can’t read it, I can understand a very small part, and I know how to do it, but there are very few!"

Seeing his serious expression in Yu Fa, everyone asked suspiciously, "Isn't it such an exaggeration?!"

Hey...You haven't seen it before, and you still don't understand Xu Cong's greatness. Let's use facts to conquer you.

Yang Kaixuan ignored these people, stood beside Xu Cong's bed in front of them, and whispered to Xu Cong, "Xu Cong, I have a question for you, do you have time?"

Xu Cong saw Yang Kaixuan come to him, so he turned his head and put down the headset, and accepted the question he handed over.

topic:

Let P be a point on the long axis of an ellipse (x²/25)+(y²/16)=1, and the slope of the passing point P is the k-line intersecting the ellipse at two points.

If the value of |PA|²+|PB|² depends only on k and has nothing to do with P, find the value of k.

After reading the question, Xu Cong sat up, and at the same time stretched out his hand and said to Yang Kaixuan: "Paper and pen."

As soon as Yang Kaixuan heard Xu Cong's words, he immediately delivered the things to Xu Cong.

After Xu Cong got the pen and paper, he started to write while talking.

The calculation process seems to be a few simple steps, but the values ​​involved are too big, and all kinds of a²k² are numerators and denominators.

Xu Cong explained the whole process of this question carefully to Yang Kaixuan.

"`According to the above..."

lPA|²+lPB|²=(x₁-a)²+y₁²+(x₁-a)²+y₂²"

Then untie it, set 512-800k²=0, and then get k=±4/5. "

In Xu Cong's mouth, what this question says is a lightness.

But when everyone looked at this step, they were dumbfounded!

Just the score multiplied by one of the steps (k²+1) caused them a headache.

Molecule: (512-800k²)a²+800(16+25k₂)

Denominator: (16+25k²)²

When Xu Cong listed these, the calculator was useless, so he wrote the steps on the sketch paper and drew the picture, and then he gave the answer!

Everyone looked at the densely packed formulas and answers, and tremblingly said, "We all understand the truth, but Xu Cong, did you just give the answer?"

"We are calculating step by step on the performance paper, and we can't be sure that everything is right, you, this is too scary!"

"Damn! Even if you are mentally prepared, even if you have tried to get used to it, you are still shocked, OK!"

"Xu Cong, you are too perverted!"

Several people almost roared out, and their voices frightened the brothers in the bedroom next door.

Xu Cong ignored them. After speaking, he handed Yang Kaixuan the test paper and parrot paper, and then continued to look at his mobile phone as if he was okay.

Everyone: "The mentality collapsed!!!"

Yang Kaixuan didn't sigh too much, and after getting the answer, he went back to his bed and looked at it seriously.

It's not just the process, but also Xu Cong's problem-solving ideas.

Why did Xu Cong use this method?

This is the key to Yang Kaixuan's learning. One question and one answer.

The other roommates were just like air, ignored.

This is the gap between them at this moment. Yang Kaixuan has already understood that Xu Cong's talent is something he cannot catch up. Only by constant humility and learning can he close this distance.

Yang Kaixuan did two class evenings for a test paper for the Olympiad and had not finished his self-study. After that, he took it to the dormitory and did it for a long time.

While doing it, he had to ask Xu Cong at the same time, after all, there were many questions in it, and he wouldn't know it.

"Xu Cong! Here..."

"Xu Cong, the idea of ​​this question"

"Xu Cong..."

Finally, it was finished. Xu Cong couldn't hold back his urine. When he got out of bed and went to the bathroom, he saw the answer to Yang Kaixuan's last question.

"Wrong, wrong..." Xu Cong said casually.

Fuck!!!

f*ck! !

Puff! !

Yang Kaixuan worked so hard for an hour, Xu Cong finally said that he was wrong, and he denied it!

If the heart is not good and the blood pressure is high, it will pass directly!

If Yang Kaixuan had not experienced it so many times, he would have passed by too. He quickly took a deep breath to keep himself calm.

"Then your idea is...?"

Yang Kaixuan patiently asked Xu Cong for advice.

Xu Cong is also very anxious at this time. After all, people have three anxiousness, and no one can withstand it when they come.

So he waved his hand and quickly said to Yang Kaixuan: "Wait when I come back from the toilet, wait a moment."

The title of this question is:

Let i₁, i₂, L, i₁₀ be an arrangement of 1, 2, L, and 10, denote S=li₁-i₂l+li₃-i₄｜+L+li₉-i₁₀l, find all the possible values ​​of S.

Although the number of inscriptions is very small, but the amount of information is a lot, but you can't get started!

However, many people feel like they are dying when they see the question.

If this compares the subject to a mountain, then this is Mount Everest!

Yang Kaixuan looked at his watch and shouted to Xu Cong: "Xu Cong, there is almost no time! The lights will be turned off soon..."

Xu Cong said to him indifferently: "It's okay, I'll talk to you verbally later."

Oral calculation?

!!!

Puffy!!!

Xu Cong, do you know what you are talking about? You actually want to reckon with Mathematical Olympiad?

And it's an additional question in the Olympiad! This is the final additional question!

"This question is relatively simple, don't worry, wait for me to come back."

As soon as Xu Cong ran out to go to the bathroom, the lights in the dormitory went out.

Yang Kaixuan was also speechless, he was too difficult.

The roommates felt uncomfortable listening to the conversation between the two. Now their dormitory has been divided into three levels.

Xu Cong ranks first, Yang Kaixuan is second, and they are third.

...:

When Xu Cong came back from the dark, the roommates were all lying on the bed, and they were all ready to sleep.

Xu Cong climbed onto the bed, connected the mobile phone to the charger and put it aside, and then he started to talk to Yang Kaixuan, directly based on the impression of the shocking glimpse just now.

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