Oh no! I've only been a freshman and I've already been targeted by a mean upperclassman.

Chapter 152 Notes!

My phone vibrated.

Group 302.

[Wang Qiang: Have you even entered the school gate yet??? I'm dying of advanced calculus, come save me!!!]

Li Chen is typing.

[Li Chen: I'll be there in ten minutes. Turn to Chapter 3.]

[Wang Qiang: Really??? You're going to teach me???]

[Li Chen: My sister-in-law said so.]

The group was silent for five seconds.

[Wang Qiang: Long live sister-in-law!]

[Chen Mo: Sample #197 has been entered. Note: Yan Xi's management authority over dormitory 302 has been upgraded from "indirect intervention" to "academic planning and supervision."]

[Zhao Zixuan: Speak like a human being.]

[Chen Mo: My sister-in-law has started paying attention to our grades.]

Li Chen locked the screen and quickened his pace to cross the east gate.

Raindrops still clung to the leaves of the sycamore trees. They felt slightly slippery underfoot.

He took twenty steps.

He took out his phone.

I sent a message to Yan Xi.

[Li Chen: I'm inside the school gate.]

Nine seconds.

[Yan Xi: Changing clothes. Taking photos.]

He took another ten steps.

[Li Chen: Xi Xi.]

Yan Xi: Mm.

[Li Chen: Thank you for today.]

Twelve seconds.

Yan Xi: You've been preparing for much longer.

Li Chen put his phone back in his pocket.

The warmth of her fingers still lingered in the pocket.

302 Dormitory.

When Li Chen pushed the door open, Wang Qiang had already spread his advanced mathematics textbook on the table.

Turn to Chapter 3. Limits and Continuity.

The pages were as clean as if it had just been bought.

Are you sure you've flipped through this book?

Wang Qiang looked aggrieved.

"Turn it over. Turn the cover over."

Zhao Zixuan sat on the upper bunk, his legs dangling over the ladder.

"I went through the catalog."

Chen Mo pushed up his glasses.

"Based on the analysis of the wear and tear and frequency of use of his textbooks, Wang Qiang's total time spent flipping through his calculus textbooks this semester did not exceed forty-five minutes."

"Thirty minutes of that occurred during the first week of school, and the motivation was to 'pretend to be diligent'."

"The remaining fifteen minutes were distributed before three in-class quizzes, and the behavior pattern was 'flipping to the example questions and copying directly'."

Wang Qiang turned and glared at him.

"Are you monitoring how I read books?"

"You sigh every time you turn the page. The frequency is negatively correlated with page-turning speed. The faster you turn the pages, the heavier the sigh. The data is very significant."

Li Chen opened the wardrobe. He changed out of his inner layer and took out a clean gray sweatshirt to put on.

The phone is on the table.

He picked it up and took a picture.

The gray sweatshirt in the mirror had a neat collar and clean cuffs.

Send it to Yan Xi.

Four seconds.

Yan Xi: Okay.

He locked the screen. He walked to Wang Qiang's desk and opened the textbook to the first section of Chapter 3.

"Where not?"

"Where to begin..." Wang Qiang's gaze lingered on the page for eight seconds. "Start with the ε-N definition of the limit of a sequence."

That was the first definition.

"right."

Li Chen tapped the page with his finger.

"Listen carefully. I'll only say it once."

The next forty minutes.

Li Chen used a whiteboard marker to derive the entire framework of the limit theory on the glass plate on Wang Qiang's desk.

He speaks quickly.

But the logical thread is clearly laid out. Each theorem is first presented with intuition, then with a rigorous proof, and finally with common question patterns.

Wang Qiang's expression went from blank to half-understanding to nodding frequently.

Zhao Zixuan climbed down from the top bunk at some point and moved a chair to sit next to him.

Chen Mo took out his notebook and began to take notes using his own symbol system.

"Wait a minute," Wang Qiang raised his hand to interrupt. "L'Hôpital's rule, can it be applied to zero to zero and infinity to infinity?"

"It can be used, but there are prerequisites. The numerator and denominator must be differentiable in the punctured neighborhood, the derivative of the denominator must be non-zero, and the limit value must exist or be infinite. If any of these conditions are missing, it cannot be used."

"What about question seven from the last assignment—"

"Zero to zero. Use it directly. You can use Taylor if you want, but L'Hôpital is faster."

Wang Qiang drew a circle in the book.

"Now that you say that, I feel like I can live."

Zhao Zixuan crossed his arms and leaned back in his chair.

"You explain things more clearly than the teacher."

"Because the teacher has to lecture for 90 minutes. I'll only cover the topics you'll be tested on."

Li Chen put down his pen.

That's all for today. Go home and do exercises 1 to 15 on your own. I'll check them tomorrow.

"Assigning homework today?"

"Yan Xi asked me to help you pass. I agreed. I won't be able to explain it to you if you fail."

Wang Qiang's expression changed.

"Your sister-in-law will let you—"

"Help him catch up on the material, so he doesn't fail."

The dormitory was silent for two seconds.

Wang Qiang slowly stood up.

He clasped his hands together in prayer, facing the direction of the void.

"I will never forget my sister-in-law's great kindness and virtue."

Zhao Zixuan patted the back of his head.

"Alright, alright. Stop praying. Go do your homework."

Li Chen returned to his desk.

turn on computer.

He wasn't just casually mentioning organizing his physics notes. He created a new folder named "Physics - Electromagnetism".

Then I opened Chapter 3 of the textbook, and, referring to the PPT and the textbook, began to organize it page by page.

There was silence for twenty minutes.

The phone lit up.

News about Yan Xi.

[Yan Xi: Where are your notes organized?]

Li Chen glanced at the progress on the screen.

[Li Chen: Chapter 3, Section 2. Coulomb's Law and Electric Field Strength.]

[Yan Xi: Gauss's theorem in the third section is the key point. It was the subject of two major questions on last year's exam.]

Li Chen flipped through the past years' final exam questions.

Indeed. The application of Gauss's theorem has been tested for two consecutive years.

[Li Chen: How do you know the past exam questions for our physics department?]

Seven seconds.

[Yan Xi: I also studied physics in my freshman year.]

[Li Chen: You architecture students study physics?]

[Yan Xi: Elective. I chose it.]

[Li Chen: Why?]

Four seconds.

[Yan Xi: Because it's useful.]

Li Chen stared at those three words.

She took physics as an elective in her freshman year. She was an architecture student, and the coursework was already heavy. She also took an additional introductory engineering course.

"Because it's useful."

This sentence roughly translates to: She started preparing for future fields such as structural mechanics, optical environment simulation, and building physics during her freshman year of college.

He continued typing.

[Li Chen: What was your score on the Physics exam?]

Eleven seconds.

[Yan Xi: Guess.]

[Li Chen: 98.]

three seconds.

[Yan Xi: 99. One point deducted for calculation. A negative sign was omitted when carrying over.]

Li Chen put down his phone.

He took a deep breath.

I glanced at Wang Qiang, who was struggling with example problems. Then I looked at my own half-finished notes on my computer screen.

"What's wrong?" Chen Mo noticed his expression.

"My girlfriend is a 99-year-old."