The next day, in order to express his gratitude to Senior Sister Chen, who introduced this part-time job to him, Lu Zhou decided to invite her to dinner.

However, on the question of whether to eat yellow braised chicken or KFC, he was again entangled.

So, he asked Liu Rui, another living person in the dormitory, for his opinion.

Liu Rui, who was in a double row with netizens, was sent back to the spring by the opposite side, and he was annoyed at the moment, and he didn't listen carefully to Lu Zhou's question, and replied casually without looking back: "Malatang, cheap and affordable!" ”

And then......

Lu Zhou really invited.

In the snack street at the school gate, at the door of the mountain city Malatang, Chen Yushan, who was wearing a single ponytail, sat opposite Lu Zhou, and her tongue was stuck out by the spicy.

Although the tears were about to come out, Chen Yushan still held on, and asked while eating, "How is it?" Is my sister's math still saved? ”

Is it that spicy?

Lu Zhou threw a fish ball in his mouth with some confusion, and said while chewing, "There is still ...... Probably? Anyway, I'll do my best. ”

"Then please, my sister...... In fact, when I was in junior high school, my science grades were very good, but I ...... later Ahhh ”

Lu Zhou silently handed her a glass of water and asked, "Later?" ”

Drinking the water in one gulp, Chen Yushan stuck out her tongue cutely, and continued with a sigh of relief: "Later...... My aunt and brother-in-law have a little bit of a problem in their relationship, and the two of them are fighting for custody of Mengqi. I don't know the specific situation, anyway, now Mengqi has been with my aunt for the time being. ”

Lu Zhou nodded silently and didn't say anything.

He doesn't really want to care about other people's private affairs, in a sense, he is a very selfish person.

After eating Malatang, Lu Zhou sent Senior Sister Chen back to the vicinity of the dormitory building, and then turned around and went in the direction of the library.

On his way to the library, he received two emails.

An email from Mr. Liu is about the feedback on the data modeling assignment.

Another email was a reply from the journal "Modern Communication and Geographic Information Technology", saying that the manuscript fee had been paid to his bank card account, 150 yuan for one article, a total of 1350 yuan, please pay attention to check.

“……”

Nine SCIs are only so much money, and sure enough, it's better to make missiles than to fry poached eggs......

Lu Zhou couldn't help but sigh in his heart.

However, more than 1,000 yuan is not a lot, counting the 3,000 yuan earned by being a tutor yesterday, now the money in his card is more than 7,000, and it must be enough to pay tuition.

Originally, he planned to put it off first and make up for it at once before graduation, but now it seems that he doesn't need it.

In the next few days, Lu Zhou's life was very regular, staying up late on Mondays, Wednesdays and Fridays to eat books, and Tuesdays and Thursdays were used to consolidate his studies and preview courses in other subjects such as information technology, electronic engineering, biology, and chemistry. In addition, he did not fall behind in the practice of mathematical modeling.

Sometimes he really feels that if he can really maintain this good study habit, even without the help of the system, it will be a matter of time before he becomes a top student.

It's just that with the help of the system, this process is accelerated.

And it's like a rocket......

On Saturday, Lu Zhou, as usual, went to Ms. Yang's home to tutor Han Mengqi in math.

Maybe it was because of the accident last time, or maybe it was some kind of agreement between mother and daughter, this time Ms. Yang didn't lock the door before going to work, but just told Lu Zhou to take care of her daughter.

Watching her mother go out with an expressionless face, Han Mengqi looked at Lu Zhou: "Then, let's start." ”

With that, she turned around and went back to her room.

Following Han Mengqi's footsteps into the room, Lu Zhou unexpectedly found that she hadn't seen her for a week, but this time she had tidied up the room.

Without any superfluous communication, Han Mengqi spread out the book on the table, turned to the page in the corner, and looked at Lu Zhou.

"According to the outline you gave me, I have seen the analytic geometry of the second compulsory course...... And then what? ”

"And then?" Lu Zhou raised his eyebrows and asked with a smile, "What did you say first?" ”

"There's nothing I don't understand, it's pretty simple." Han Mengqi raised her little head and said impatiently, "And then?" ”

"Then I'll test you," Lu Zhou took a piece of A4 paper from the side and wrote on it with a pen.

[In the Cartesian coordinate system xoy, the left and right focal points of the ellipse C1: x²/a²+y²/b²=1(a>b>0) are F1 and F2, respectively. where F2 is also the focal point of the parabola C2:y²=4x, and the point M is the focal point of C1 and C2 in the first quadrant, and |MF2|=5/3。 Find the equation for C2. 】

After writing this question, Lu Zhou made a gesture of please.

Han Mengqi's eyebrows jumped slightly, she said a big thing just now, she didn't expect Lu Zhou to test her on the spot.

Gritting her teeth, she picked up the pen and thought for a long time on the scratch paper.

As a result, ten minutes passed, and only the first step was solved.

i.e. –

[Obtained from C2:y²=4x, F2(1,0).] 】

After waiting for about ten minutes, Lu Zhou looked at his watch, smiled and said, "In the college entrance examination, you are only allowed to think about a question for ten minutes at most. Now, you can only get three points at most for this question. ”

"Hmm......" Han Mengqi gritted her teeth and looked unconvinced. However, this is the way to solve the problem, sometimes the more you are in a hurry, the more you can't solve it.

Lu Zhou smiled, flipped out a paper from the pile of materials next to him, pointed to the position of the penultimate question, and continued: "And the most important thing is that this question is what you missed on this paper." ”

“…… You bullied me. Han Mengqi threw away her pen, glared at Lu Zhou angrily and said, "I know I'm stupid." ”

"I'm just teaching you, and I've never said you're stupid, on the contrary, I'm optimistic about your cleverness, so please don't be presumptuous." Lu Zhou picked up the pen she dropped and wrote the rest of the process on A4 paper, "The key to this kind of problem is to determine the value of M, so the second step must be set M(x1, y1), and according to |." MF2|=5/3 and M2 on the parabola C2......"

"Our second goal is to find the half-focal length of the ellipse C1, solve this step, and the rest of the problem becomes a problem of understanding the system of equations."

Lu Zhou wrote down the key to each step on paper and clarified the idea of solving the problem.

At first, Han Mengqi looked impatient, but then stared at the paper with a look of seriousness.

Eventually, a hint of realization appeared on her face.

The small mouth moved slightly, and Han Mengqi, who was staring at the scratch paper intently, frowned, nodded thoughtfully, and said, "So that's ......."

"Your teacher must have said it, but you haven't heard it at all."

"Our teachers...... I don't have to go into detail with you. Han Mengqi said reluctantly.

Lu Zhou was happy: "You might as well say this to your math teacher, let's see if we can make him angry to death." ”

Han Mengqi's teeth itched angrily, but she couldn't do anything about him, so she had to snort.

"No wonder my sister said you, you speak very meanly......"

Lu Zhou: ???

Someone is saying bad things about me behind my back?

I can't pretend I didn't hear that.

Lu Zhou coughed, disconnected the topic, and said while picking up the pen: "This problem is a typical intersection problem to find elliptic equations, I believe that the next time you encounter this type of question, you can get at least half of the points." ”

"And half of it?" Han Mengqi tilted her head and asked.

"Half of the score is on the second question, which is usually combined with vector questions in the college entrance examination, so there is usually a second question ......"

As he spoke, Lu Zhou continued to write at the end of the stem.

[The point N on the plane satisfies the vector MN=vector MF1 + vector MF2, the straight line l∥MN, and C1 intersects at two points A and B, if the vector OA*OB=0, find the equation of the straight line l. 】

The moment she saw the question, Han Mengqi was completely stunned and looked at Lu Zhou helplessly.

However, Lu Zhou didn't look at her, but sat on the edge of the bed, picked up the workbook on the side, and looked for the next example problem.

"You try to do it first, if you can't do it, I'll teach you, it's fifteen minutes, let's start."

is even worse than the first question, this time Han Mengqi only wrote out one solution, and none of the rest of the things were correct.

I don't know if it's because she has a sister who is about the same age, Lu Zhou didn't feel very impatient, nor did he mock her for being another "sending a question", but patiently explained to her the idea and process of solving the problem.

Looking at the steps on the scratch paper, Han Mengqi's eyes widened, and she whispered, "It's amazing......"

"The process of my study is to keep summing up, summing up experience from mistakes, I hope you find out the questions you don't usually know, it's best to copy them in a notebook by hand, and then I will explain them to you every week," Lu Zhou returned the question to Han Mengqi, and said casually, "The wrong questions are necessary for learning mathematics, and even all science, if you want to learn science well, you must prepare." Just like ADC going out with Dolan, auxiliary with eyes, are all basic operations. ”

Han Mengqi's eyes lit up, and she immediately became interested, and interjected: "You also play masturbation?" Which district? My Nurse Thief 6! ”

“…… Blackberries. ”

"I'll add you as a friend! Give me your Q number...... Ouch! ”

Lu Zhou stretched out his hand and knocked on her forehead, looked at her who was covering her forehead, and said angrily: "Still playing games, wait until you score 100 points in mathematics this month!" ”