On the way to the airport, Qi Yi said that he wanted to give Yan Yun a gift, and then took a pen and wrote down an equation in the notebook he carried, 17·x^2-16|x|y+17y^2=225.

"It's been a long time since I've done a problem with you, this relatively simple equation is for you, I'm not in Melbourne, you can solve it when you're bored." Qi Yi tore off the paper on which he had written the equations from his notebook.

"Okay~ However, I haven't known what mathematics is for a long time, and I feel that even if mathematics still knows me, I don't know mathematics anymore, so I'll give it a try. Yan Yun smiled and took Qi Yi and handed her all the paper.

"Bao Bao, isn't there a bit of a problem with the brains of the two people in the back, how can anyone make a gift with a mathematical formula? What's even more exaggerated is that there are still people who are very happy to receive it. Shen Xi felt that the two people in the back seat were wonderful.

"Wait for me to take a look when I have time, I can't figure out the two people in the back, and after eating 'P', I will send 'fart'. Bao Bao suddenly aligned himself and was a little curious about what kind of equation he had written.

"Bao Bao, have you become an alien like the two of them? Shen Xi was a little depressed, Bao Bao was actually interested in a mathematical formula.

"Eh, Bao Bao, were you a science student before? How do you even know 'fart'?" Yan Yun has the impression that the School of Journalism and Communication of Xiamen University only accepts his own major in arts and sciences, and Bao Bao does not accept science students in journalism.

"No, I used to love the phrase "I think, therefore I am," and I liked the philosopher Descartes.

Then one day I heard our math teacher say that Descartes was the father of analytic geometry.

Our teacher then told a love story about Descartes and a Swedish princess.

It didn't take long for me to find out that this touching love story was fake.

Forget if the story is fake, then what Descartes's love curve, what is drawn as a heart, but it turns out to be a strange ass shape.

I felt speechless when I read it, if that story is true, send a 'fart' to someone, it's strange that it can have a good result. Bao Bao explained what he meant by 'fart'.

If Qi Yi really sent a "fart" to Yan Yun, he would definitely be despised by Bao Bao.

"Unfortunately, you may be disappointed, but I still remember Descartes' equation ρ=a(1-sinθ), which has no similarity with the one that Qi Yi just wrote. You have to be interested in the equations, and you can solve them when you get home. Yan Yun directly answered Bao Bao's question.

"Do you all know Descartes' love curve?" Qi Yi was a little surprised when it was his turn.

"Do you still have a philosophy class at university?" Qi Yi asked Yan Yun.

"No, I remember reading Descartes's "Metaphysical Meditations" at that time, and later when I was in analytic geometry class, I heard the teacher say that analytic geometry is based on Descartes' plane Cartesian coordinate system, and then I happened to see this equation of love from him, but I didn't see a heart pattern that looks like an ass. Yan Yun replied.

"Descartes was first a philosopher and then a mathematician.

What Descartes wanted to do was to turn any mathematical problem into an algebraic problem, and then reduce the algebraic problem to solving an equation.

The prophets of that day seemed to be all-powerful, and Descartes was still a theologian. Qi Yi then explained Descartes' geometric assumptions.

"Can you still talk, can you speak! Believe it or not, I'm going to get you out of the car one by one. Shen Xi felt that there was no way for her to continue to stay in such a discussion, not even for a minute.

"You've just drunk more than a bottle of wine by yourself, are you sure you can go back to Eureka on all fours after you've kicked us all out of the car?" Yan Yun especially liked to watch Shen Xi go crazy from time to time.

"I'd rather have unsound limbs, okay!" Shen Xi's face was full of unhappiness.

"That's not good, you're not sound, the last people to hurt are Bao Bao and me, I have no interest in helping Bao Bao take care of you who can't take care of yourself. Yan Yun gave Shen Xi a look of disgust.

"Yan Xiaoyun, are you itchy skin, who do you say can't take care of themselves?" Shen Xi's expression had changed from unhappy to angry.

"Who is so bad that you dare to say that you can't take care of yourself? I don't remember who said that, I just raised a small question about the fact that you can drive. Yan Yun didn't admit it.

Along the way, Bao Bao barely spoke again.

Whether Yan Yun and Qi Yi want to choose to be together or not is something that the two of them need to face by themselves, as friends, she has persuaded and persuaded what she should have said, and this is enough.

"Don't you really get out of the car to send your school grass?" After arriving at the airport, Bao Bao asked Yan Yun.

"Well, if I don't go, I will cry when I wait for the province, and I will be responsible for buying paper towels, paper towels are made of wood, wood needs to be cut down trees, cutting trees will cause global warming, in order not to put too much burden on the earth, I will not get out of the car. Yan Yun likes to tell some strange truths in a twist and turn when he is particularly sad.

It seems that if the truth is said too much, the sadness will not be so obvious.

"On behalf of the United Nations Environment Programme, I would like to express my sincerest gratitude to you. Qi Yi replied to Yan Yun with a smile, and then prepared to get out of the car and go to the trunk to get his luggage.

"Are you really not even going out of the car door?" Shen Xi felt a little incredulous.

"No, what are you doing going out, it's a big night, I'm such a big beauty, it's not safe to get out of the car. Yan Yun said very calmly.

"Yan Xiaoyun, you still have to be shameless, shameless. Shen Xi had the urge to run to the back seat to grab Shen Xi.

"The face is used to see, not to be asked, and the meal is also used to eat, only someone as special as you will ask for a face for a while, and a meal for a while. "Yan Yun takes it as his responsibility to fight Shen Xi.

"When am I going to ask for food?" asked Yan Xi through gritted teeth.

"Just now, didn't you ask Mrs. Chef for a bowl of rice?" Yan Yun asked Shen Xi as if he couldn't remember clearly.

Shen Xi got out of the car directly from the co-pilot's position, ready to sit in the back seat to scratch Yan Yun down.

When Shen Xi was about to enter the door, Qi Yi also took his luggage and walked to the door of the back seat, and Qi Yi stopped Shen Xi very kindly.

"You don't want to be as knowledgeable as Yan Yun, she can eat so much, she must have more food than you when she asks for food. Qi also appeased Shen Xi so that Yan Yun would not suffer when he just left.

Qi Yi opened the co-pilot's door, and after Shen Xi sat back, he turned back to find Yan Yun, who was still sitting in the back seat.

"You remember to solve the equation, I'll give you more interesting after you solve it. Qi Yi didn't mean to say goodbye to Yan Yun directly.

"Okay. Yan Yun handed the dessert he had packed at Brunetti in the morning and handed it to Qi Yi.

Yan Yun looked at Qi Yi and didn't say anything else.

What Yan Yun has in his eyes now is the deepest part of Qi Yi's memory, the eyes that can soothe his heart.

When there was no warning and no preparation, the parting quietly and without saying goodbye was the tacit understanding that Yan Yun and Qi Yi already had without communication.

There are many ways to part, Yan Yun and Qi Yi chose the one that makes each other the least sad.

No goodbye, no parting.