The book-crossing case happened! The villains all want me to go to jail

Xie Xuan'an finally returned to the dormitory after being missing for a long time. In the dormitory, the moment Su Yi saw Xie Xuan'an, she rushed over like a whirlwind and hugged him tightly, crying:

"You're finally back. I really thought I'd never see you again."

Later, because the final exam was approaching, Xie Xuan'an didn't want to fail, so Su Yi helped him review with all his strength.

In the spacious and bright classroom, the afternoon sun shines through the windows, shining warmly and softly on the desks, dividing the desktop into light and dark areas.

Xie Xuan'an sat quietly in his seat, brows furrowed, holding the advanced mathematics textbook tightly in his hands, his eyes fixed on a complex function differentiation problem.

"Su Yi, I really can't understand this function differentiation theorem." Xie Xuan'an turned his head, his eyes full of confusion and helplessness, and looked at Su Yi who was sitting next to him with a pleading look.

Su Yi put down the notes he was sorting out, and his eyes shot like an arrow towards the question Xie Xuan pointed out. His eyes instantly became focused and sharp, as if he wanted to shoot this difficult question through his heart.

"Xuan, don't worry, let's do it step by step." Su Yi picked up a piece of chalk and strode to the blackboard. "Look, this problem first requires the use of the chain rule." He said as he wrote down the key formulas and steps on the blackboard.

Su Yi's hands moved quickly on the blackboard, and the friction between the chalk and the blackboard made a "squeaking" sound, which was particularly clear in the quiet classroom.

However, when he was halfway through his speech, Su Yi's voice suddenly stopped. He looked away from the blackboard and looked at Xie Xuan'an, his eyes reddened without knowing when.

Xie Xuanan noticed Su Yi's strangeness, and a wave of guilt and emotion surged in his heart. He gently patted Su Yi's arm, his eyes full of understanding and comfort.

Su Yi sniffed and tried to calm herself down. "Xuan, it's not your problem, it's me... I think of the days when you disappeared, and I was really worried. I was afraid that I would never be able to study with you again and discuss these topics with you."

A hint of determination flashed in Xie Xuan'an's eyes. He held Su Yi's hand tightly and said, "Su Yi, I'm back. I'll be here from now on."

With Su Yi's patient explanation, Xie Xuan'an gradually understood the solution to the problem, and a smile of relief appeared on his face.

"Thank you, Su Yi. If it weren't for you, I don't know how long I would be stuck on this problem." Xie Xuan'an said gratefully.

"We are brothers, there's no need to thank me." Su Yi also smiled, and the tears in his eyes turned into joy.

The sunlight in the classroom was still warm, shining on the two of them, as if giving their friendship a layer of golden light.

Some of the other students in the classroom were discussing problems in a low voice, while others were concentrating on doing their homework, but Xie Xuan and Su Yi seemed to be in a small world that belonged only to them.

The bell for the break just rang, and the originally quiet classroom suddenly became lively. Some students chatted in groups of three or five, with laughter coming one after another; others couldn't wait to walk out of the classroom to relax.

However, in the corridor outside the classroom, Xie Xuan'an and Su Yi had no intention of enjoying this moment of relaxation. Xie Xuan'an was holding a math workbook in his hand, his brows furrowed, and his face was full of confusion.

"Su Yi, I'm still not quite clear about the solution to this proof. I assumed the proof by contradiction, but I always make mistakes when reasoning." Xie Xuan'an pointed to a question in the exercise book and asked anxiously.

Su Yi leaned over to take a look at the question. After thinking for a moment, he picked up a pen and wrote down a few key steps on Xie Xuan'an's notebook.

"Xuan, you see, we can start with this condition for this question." Su Yi explained while writing.

However, when he got to the key point, his voice suddenly became choked. He raised his head and looked into the distance, his eyes gradually reddening.

Xie Xuan'an was startled by Su Yi's reaction. He asked with concern: "Su Yi, what's wrong with you?"

Su Yi turned around and looked at Xie Xuan'an, her eyes full of affection. "Xu'an, you don't know, during the time you were away, every time I saw a math problem, I would think of the days when we studied and discussed together. I'm really afraid that there will never be such an opportunity again."

Xie Xuan'an was touched. He put his arm around Su Yi's shoulders and said, "No, it will always be there in the future."

Under Su Yi's patient guidance, Xie Xuan'an finally understood the idea of ​​this proof question, and a happy smile appeared on his face.

"Su Yi, thank you so much!" Xie Xuan'an said excitedly.

"You're welcome. Let's keep working hard and strive to get good grades in the final exam." Su Yi also smiled, and the haze in his eyes disappeared.

Students were coming and going in the corridor, but Xie Xuan and Su Yi seemed to be in a mathematical world that belonged only to them, focused and persistent. On one side of the corridor, several students were chasing and playing, but they were not affected at all.

The library is exceptionally quiet on weekends, with only the occasional sound of turning pages and light footsteps.

Xie Xuan and Su Yi sat at a table in the corner, which was piled with various math books and notes.

Xie Xuanan held a probability theory textbook and muttered quietly: "Su Yi, I am always confused about the concepts in this probability theory."

Su Yi put down the reference material he was reading and looked at Xie Xuan'an, his eyes full of patience and care.

"Xuan, don't worry, let's sort it out one by one." Su Yi gently opened the textbook in Xie Xuan'an's hand and pointed to one of the concepts.

At this moment, Su Yi's eyes suddenly turned red.

Xie Xuanan felt very upset when he saw Su Yi's expression. He held Su Yi's hand and said, "Brother, I understand how you feel."

Su Yi took a deep breath, tried to adjust his emotions, and continued to explain to Xie Xuan'an.

With Su Yi's patient explanation, Xie Xuan'an gradually gained a clearer understanding of the concept of probability theory.

"Su Yi, I seem to understand a little bit." A confident smile appeared on Xie Xuan'an's face.

"Great, then let's consolidate it." Su Yi also smiled, his eyes full of relief.

The light in the library was soft and warm, shining on them, as if witnessing their deep friendship and common efforts.

In the evening, the breeze blew gently on the playground, bringing a hint of coolness. Xie Xuan and Su Yi walked side by side, and the afterglow of the setting sun stretched their shadows very long.

"Su Yi, is there any general solution to this kind of series limit problem?" Xie Xuan'an asked as they walked.

Su Yi stopped and thought for a moment. "Xuan, generally speaking, you can consider..."

Suddenly, Su Yi's voice became choked. He raised his head and looked at Xie Xuan, tears flashing in his eyes.

Xie Xuan'an felt a pang in his heart. He stopped, faced Su Yi, and said, "Su Yi, don't be like this. I'm always here."

Su Yi nodded, wiped his eyes, and continued to explain to Xie Xuan. Under Su Yi's patient guidance, Xie Xuan had a deeper understanding of the solution to the limit of the series.

"Su Yi, thank you. I feel like I have made progress again." Xie Xuan'an said gratefully.

"You're welcome. Let's work hard together!" Su Yi said with a smile.

Some of the students on the playground were running, some were playing, but Xie Xuan and Su Yi were immersed in the world of mathematics. Their friendship became even more precious in the afterglow of the sunset.

At noon, the cafeteria was bustling with people, filled with the aroma of food and the laughter of students. Xie Xuanan and Su Yi finished their meal and found a seat in a corner.

Xie Xuan'an had just taken a few bites of rice when he suddenly put down his chopsticks and said with a distressed look: "Su Yi, I don't think I remember this knowledge point of integral calculation."

Su Yi put down the spoon in his hand and looked at Xie Xuanan. "Xuanan, don't worry, I'll tell you again."

However, as he spoke, Su Yi's eyes turned red.

When Xie Xuanan saw Su Yi's expression, he was filled with emotion and guilt. He gently stroked the back of Su Yi's hand and said, "Su Yi, it's all my fault."

Su Yi shook his head, tried to force a smile, and continued to explain to Xie Xuan'an.

With Su Yi's patient explanation, Xie Xuan'an finally recalled the knowledge points of integral calculation.

"Su Yi, I understand, thank you!" Xie Xuan'an said happily.

"Okay, let's eat quickly, and then we'll review other things after dinner." Su Yi said.

The cafeteria was still noisy, but Xie Xuan'an and Su Yi's hearts were closely connected as they worked hard together for the final exam.

But there is always someone spying in secret.