Immediately after that, Professor Zhang opened the advanced mathematics on the lecture table, raised his head and looked at us below and said, "Please open the first page of the textbook, and we will start with functions, parametric equations and polar coordinates. ”。

After Professor Zhang said this, she turned around gracefully 180 degrees again, and wrote down the words "functions, parametric equations and polar coordinates" on the blackboard.

Then he looked at us again and asked, "In the formal class, I would like to ask you a question, what is a function?" ”

Regarding Professor Zhang's question, none of the students present spoke, probably for fear of making a mistake!

Seeing that no one answered, Professor Zhang must have understood, so she smiled and said in an encouraging tone: "You can speak freely, boldly say your thoughts, don't be afraid to make mistakes, study, just don't learn if you don't understand." ”

After Professor Zhang said this, the class leader Wang Hao was the first to stand up and said: "I think the function is defined as a mapping between sets of non-empty numbers. ”

After Wang Hao finished speaking, Professor Zhang smiled at him and motioned for him to sit down.

"Are there any other answers?" Professor Zhang asked in the aisle between classes.

"I think of a function as an equation with unknown parameters." A chubby male classmate stood up and said.

Professor Zhang smiled again and motioned for the chubby male classmate to sit down.

"Is there a different answer?"

There was silence again.

Hu Die took advantage of Professor Zhang's inattention, turned to look at Zhang Yueming in the back seat of me, and said with a smile: "Hey! What the hell! Didn't you say you were a genius? Do you know this question? ”

Zhang Yueming looked super confident and said, "This is so easy." As soon as he finished saying this, I don't know if Professor Zhang heard it at the tip of his ear, or what, so he directly called Zhang Yueming's name and said, "Come on." What is a function? ”

Hu Die didn't hold back for a while, and then burst out laughing, because it was an instinctive reaction, the volume was not effectively controlled, and this sound overshadowed all the sounds in the classroom.

Everyone's eyes once again focused on Hu Die's body, including Professor Zhang standing on the three-foot podium.

Although Professor Zhang's eyes were unusually sharp when he looked at Hu Die, Hu Die's face was calm and calm, as if nothing had happened.

The only fortunate thing is that Professor Zhang just gave Hu Die a sharp look, and didn't say anything else.

After the air in the classroom was quiet for a few seconds, Professor Zhang motioned for Zhang Yueming to answer the question, and Zhang Yueming said with a relaxed face: "The concept of a function is to give a set of numbers A, assuming that the element in it is x, and apply the corresponding rule f to the element x in A, which is denoted as f(x), to get another set of numbers B, assuming that the element in B is y, then the equivalence relationship between y and x can be represented by y=f(x)."

This answer was affirmed by Professor Zhang.

This guy looks dumbfounded on the surface, but judging from his answers, his brain is quite clear and understandable, because his definition of functions is not from the script, but his own understanding of the language of combinations, and I dare to conclude that this guy's high numbers should not be very bad. Thinking of this, I don't know why I have an inexplicable joy.

The pace of classes in college is really flattering, at least for me as a freshman. Professor Zhang stood on the three-foot podium and said cracklingly, and I didn't even digest some knowledge points in time, so I jumped by. The whole brain is dizzy, and those who feel the same way as me are Hu Die and Li Muling who are sitting next to me.

Seeing Xiang Shanshan, who had a calm face and kept wandering on the tip of the pen, I couldn't help but ask, "Shanshan, don't you feel dizzy?" ”

Xiang Shanshan smiled slightly: "It's okay, I feel that Mr. Zhang's talk is not very deep, and it is all the most basic content."

When Xiang Shanshan said with such a relaxed face, I, Li Muling, and Hu Die all looked at her with stunned expressions.

I've always felt that I'm good at math and I like math, but today, I'm completely inferior.

"Anyway, I'm very dizzy," Li Muling pouted.

Hu Die simply closed the advanced mathematics textbook and said helplessly: "These formulas or something, it knows me, but I don't know it." Come on, sister, I'll continue to chase the novel "My Science and Engineering Boyfriend" by fool Zhang, relax! ”

After speaking, Hu Die took out the novel from the schoolbag in the drawer and put it under the advanced mathematics textbook to read it.

"What good novel can a fool write, looking at the author's stupid name, I probably guessed that this novel is not good." I looked at Hu Diedao, who was reading a novel with relish.

"You don't know, this novel is the most popular youth campus novel recently, sweeping the list of major websites, you are out, hey, I won't tell you, don't disturb my sister and me to read", Hu Die didn't even look at me, and said with a disgusted face.

At this time, Professor Zhang on the podium was still crackling and talking, and I felt tired like a dog when I listened to it, but looking at Professor Zhang, I found that her old man was getting more and more energetic, which made me feel incredible.

Fifteen minutes later, the bell rang for the end of the first class, which made Professor Zhang stop.

I immediately crawled on the table and squinted for a moment.

Ten minutes of recess time passed in a hurry, and I vaguely heard the bell ringing for class, and I had to force myself to wake up.

I thought that Professor Zhang would continue to talk again with full firepower, but to my surprise, she did not lecture again, but wrote a question on the blackboard:

1. Let for any smooth directed closed surface S ∮∮ x f ( y ) dy dz + y f ( x ) dz dx - z [ b + f ( x + y ) ] dx dy = 0, where the function f ( x ) is continuous in (- ∋ , + ∋ ), and f ( 1) = a ( a, b are constants) , find f ( 2010)

My head hurt when I looked at the subject, and the tip of the pen was back and forth on the scratch paper, but I still didn't think about it. Obviously, I can't do it.

In the face of this headache of advanced mathematics, Hu Die simply gave up thinking, and Li Muling was no better, only Xiang Shanshan kept writing on the manuscript paper, which seemed to be no difficulty.

I, Li Muling, and Hu Die all looked at Xiang Shanshan, who was immersed in the topic at this time, with admiration.

"When will I be like Sanshan!" Hu Die looked at Xiang Shanshan with envy and sighed.

"I guess I don't have much chance in this life"

In the face of my blow, Hu Die snorted coldly and rolled his eyes at me.

It was at this point that a conversation behind me caused everyone to look up.

Professor Zhang: "This student, other students are doing the topic, what are you doing?" ”

Zhang Yueming: "These two questions are too simple, I would have known them a long time ago, so there is no need to waste paper." ”

Such arrogant words actually came out of the mouth of Zhang Yueming, a nerd, I was so dumbfounded, and there were all my classmates who were as dumbfounded as I was, and everyone looked at Zhang Yueming at this time like a fool.

Zhang Yueming was not surprised, with a relaxed look, I felt that he was like a sand sculpture at this time.

Professor Zhang, who was standing on the side, saw Zhang Yueming's indifferent face, and his face turned green in an instant. looked at Zhang Yueming in front of him with a black line and said, "Since it's simple, then you can go up and do it for me!" ”

Under the attention of everyone, Zhang Yueming got up from his seat and walked to the blackboard unhurriedly.

Pick up the chalk without the slightest hesitation.

One

Untie:

Let P=xf(y),Q=yf(x),R=-z[b+f(x+y)], according to Gauss's formula, the surface division of the curvature is constant zero, then the partial derivative of P to x + the partial derivative of Q to y + the partial derivative of R to z ≡ 0, so f(y)+f(x)-b-f(x+y)=0, f(x+y)=f(x)+f(y)-b f(2)=2f(1)-b=2a-b,f(3)=f(2)+f(1)-b=3a-2b f(4)=....=4a-3b .... From the inductive method, f(n)=na-(n-1)b, so f(2010)=2010a-2009b.

In less than two minutes, it was done in one go, and everyone was stunned, including Teacher Zhang who was standing on the side.

"This guy is quite showy!" Hu Die raised his head and looked at Zhang Yueming on the podium.

I didn't say anything, just an inexplicable joy in my heart.