The intern taught a top-performing class, and the parents wanted to change the homeroom teacher.

Want to take a look together?

Hearing Fang Changming say this, Meng Shuyun hesitated instead.

The math competition problems she found were exceptionally difficult.

Even ordinary math teachers can't answer this question. Even a math group leader like Fang Changming sometimes needs to rack his brains to figure it out, and there are times when he can't even answer it at all.

On the contrary, Fang Changming would occasionally consult her when he encountered difficulties.

There are four levels of problem-solving: unable to solve, struggling to solve, solving within the time limit, and solving in seconds.

The first two types shouldn't even think about competing; the third type is the norm for most competitive contestants.

The fourth type is extremely rare; they are practically guaranteed to win the gold medal.

Therefore, even for problems they know how to solve, math whizzes will gather together to discuss whether there are faster ways to solve them.

If this teacher Lu couldn't solve it, or even had no idea how to solve it, wouldn't that be embarrassing?

Meng Shuyun forced herself to come up. If she had known that Teacher Fang was entertaining guests, she would have come later.

Lu Qian noticed Meng Shuyun's micro-expression but didn't think much of it. He and Fang Changming looked at the competition question together.

"Teacher Fang, Teacher Lu, this is the question." Meng Shuyun handed over the notebook.

She copied this question by hand; the handwriting was gentle and elegant, just like the handwriting Lu Qian had seen in Li Kewei's notebook before.

"Shuyun, sit here. The three of you can discuss this slowly. I'll pull up another chair for you."

Qiao Zhaoxiang gave his seat to Meng Shuyun, then pulled up a chair and sat on the other side. After thinking for a moment, he went to the corner and took three bottles of Wahaha mineral water, placing them next to the three of them.

"Thank you, Director Qiao." Meng Shuyun said, then pulled up a chair and sat closer to the two teachers.

The treatment a sect's holy maiden receives is self-evident.

"Um……"

Looking at the question, Fang Changming fell into thought.

No, that's a bit difficult.

This question tests number theory and requires a high level of number sense and insight.

A single problem may require the application of multiple concepts such as divisibility, congruence, and prime number analysis to solve.

There is no fixed formula; even for two similar questions, the approaches can be completely different.

It really tests your inspiration!

Fang Changming secretly glanced at Lu Qian and found that the other man's expression was calm, and he was just carefully looking at the question without showing any abnormality.

I guess they're thinking about it too.

Fortunately, the problem I was given was very difficult, so it wasn't embarrassing even if I couldn't solve it.

You can also take this opportunity to discuss things with Teacher Lu for a while longer.

hiss~

Shuyun, that was a brilliant assist!

Meng Shuyun pointed at the problem with her pen and said, "Teacher Fang, Teacher Lu, this is what I was thinking. I tried modulo 3 and modulo 4 first, and found that there was no unified pattern for the parity of a and b, or modulo small prime numbers. They also couldn't be factored together... but I couldn't calculate it."

She quickly explained her thought process and then waited for the two teachers' answers.

Fang Changming fell into thought, picked up a pen and began to calculate.

Lu Qian remained motionless, seemingly deep in thought about how to solve the problem.

What he was really thinking was:

"Wouldn't it be inappropriate to say it directly, since we're on someone else's turf? Never mind, I'll pretend to be thinking and watch what Teacher Fang does."

"If all else fails, I can answer later."

"It's just friendly communication~"

After a pause, Fang Changming began to write on the scrap paper, but he kept stopping and starting, feeling that something was not quite right in his mind.

After thinking for a moment, he looked at Lu Qian, "Teacher Lu, do you have any ideas?"

Meng Shuyun also looked at the teacher from another school with curiosity.

Lu Qian's mind raced; it must be about time.

Seeing that he didn't speak, Fang Changming assumed that he was too embarrassed to speak, and said, "Professor Lu, don't be shy. We're all mathematicians. Let's brainstorm together and maybe we can solve it faster."

Meng Shuyun nodded repeatedly.

Seeing this, Lu Qian nodded, "Then let me explain my thought process. I don't know if it's correct, let's discuss it together."

"Okay!" Fang Changming handed over the ballpoint pen and scrap paper.

Lu Qian took it and began writing and explaining.

"First, write out the equation... think of it as a quadratic equation of 'a'..."

"Meng, you're not wrong in using Vieta's formulas, but you've hit a dead end. Find a way out: assume k isn't a perfect square..."

"...Now you have another root a′..."

"Continue comparing sizes... that way we can set up another equation." At this point, Lu Qian deliberately paused, waiting for the student to respond.

Sure enough, Meng Shuyun's eyes lit up, and she quickly wrote out a formula, then eagerly began to speak.

Therefore, a′ < a, and (a′, b) is also a set of positive integer solutions...

Lu Qian: "So?"

"Therefore, k must be a perfect square, and the converse assumption is not true!" Meng Shuyun's voice rose a few decibels, and her bright eyes showed the joy of solving the problem.

"Wow, it's all a setup!"

Lu Qian smiled and said, "Vieta's jump plus infinite descent can't be solved by conventional methods. The difficulty lies not in the calculation, but in the construction of the thinking."

After he finished speaking, the surroundings became quiet. Lu Qian was stunned for a moment and realized that something was wrong.

I originally planned to explain the thought process slowly, but once I started explaining the problem, I habitually used the guided teaching method and finished explaining everything in one go.

"Teacher Lu, you solved it so quickly?!"

Fang Changming stared blankly at Lu Qian, completely dumbfounded.

He was a step slower than Meng Shuyun in his reaction, only realizing the question belatedly.

Looking at the flow of this presentation, is this supposed to be a discussion? It's just a one-sided presentation!

This clearly shows that the problem was already solved before the explanation even began!

It's only been a few minutes!

We agreed to team up to run the dungeon, but you ended up soloing it!

Fang Changming hadn't felt like he was being taught in a long time.

not bad.

"Ahem!" Lu Qian coughed lightly, "I just happen to have done this kind of question before."

Coincidentally...?

Fang Changming didn't quite believe it.

This is a competition question!

Meng Shuyun was delighted, feeling that she had met a great teacher!

Then I'll ask another question!

Such opportunities are rare.

"Teacher Lu, I have one more question here, could you please take a look at it for me?"

She flipped to the previous page of her notebook, where a problem had been cut out and the solution was written below it.

Fang Changming glanced at it; it was a math problem they had discussed a few days ago. Although they had solved it, they hadn't been able to finish it within the allotted time.

He became interested, having initially thought that Lu Qian was already very good at teaching ordinary mathematics.

I didn't expect them to have such profound insights into competition problems.

"Teacher Lu, we've solved this problem, but it took too long. Could you take a look and see if there are any other methods?" Fang Changming said frankly, without a trace of sarcasm.

In the field of mathematics, the strong prevail!

"Okay, I'll give it a try."

Lu Qian picked up his pen again, thought for a while, and then began to write.

At the same time, he habitually began to provide guided instruction.

"Come on, let's look at this first..."

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