Reborn Xueba, you don't really think that studying is difficult, do you?

I saw a burst of blue flames... Ahem, that's impossible, after all, this is not Gatling.

But Yu Huatian's writing speed is really fast.

It only takes two or three breaths.

A brand new math problem is freshly released.

[The image of the known function y=f(x) is symmetrical to the image of y=2^x about the straight line y=x. 】

[g(x) is an odd function, and when x>0, g(x)=f(x)-x, then g(-8)=(??). 】

[A: -5; B: -6;]

[C: 5; D: 6. 】

This is a multiple choice question involving functions.

At first glance, it's not that difficult.

After all, is it a multiple choice question?

It's easier than short-answer questions, isn't it?
It can be seen that although Yu Huatian, the mathematics teacher, considered Lin Bei, he was not too out of line.

Instead of using a super difficult question as soon as it came up, I chose a well-regulated multiple-choice question.

but……

Although this question is quite satisfactory.

But it was aimed at top academics like Zeng Xi.

For ordinary students, it is still a bit difficult, and for the former Lin Bei, it is even more difficult.

For example, Zhang San, Li Si, Wang Teng and Zhao Dali are now dazed and sluggish.

The question does not know them, and they do not know the question. They are like parallel lines, and there is no possibility of crossing.

Even Yang Juntian frowned slightly.

It's not that he can't, but that his thinking is not very clear and it takes a certain amount of time to calculate.

however……

As soon as Yu Huatian's chalk stopped, Lin Bei said at the same time: "Teacher, the answer is C."

Zhang San Li Si: "???"

Wang Teng and Zhao Dali: "???"

Yang Juntian Lu Renchu ​​Bufan: "???"

Hearing this, everyone in the class stared at each other, with question marks on their foreheads besides question marks.

It's like Monk Zhanger who can't figure it out.

"Nani?"

"It was made so soon?"

"how is this possible?"

"What a wild guess, huh?"

Forget about Zhang San Li Si Wang Teng and Zhao Dali, they can't do it anyway for seven days and seven nights.

But Yang Juntian, Lu Ren and Chu Bufan are the top students in the class, especially Lu Ren is the representative of the math class, second only to Zeng Xi, but he hasn't even figured it out in such a short time. Answer in seconds?
If the answer is correct, it will be a hell of a time to meet Lord Hades in broad daylight.

"Pfft!"

Almost subconsciously, everyone in the class laughed.

"If I can guess right, I'll just turn my head off and kick him like a ball, ha ha!"

"I wash my hair upside down with Coke!"

"I cosplay in women's clothing!"

"I drink toilet water!"

"I collapsed on the playground!"

"I do a square dance in a Spider-Man suit!"

"I wear Sailor Moon to class!"

Suddenly, countless ruthless people set countless flags, making people exclaim that there is no most ruthless, only more ruthless.

In this regard.

Yang Juntian, Lu Ren and the others who were still counting also put down their pens, as if they were too lazy to count, and directly cursed inwardly: "Showing up the crowd, what an idiot."

As for Zhang San Li Si, Wang Teng and Zhao Dali, they all closed their eyes and supported their foreheads, worrying about Lin Bei!

Ah!
The four of them dared not look any more.

Because Lin Bei was so ashamed this time.

Fatty Wang, in particular, was anxious and annoyed when he pulled Lin Bei, "Brother Bei, my dear brother, it's really over this time, we're so bullshit, it seems like we're exaggerating!"

Obviously.

None of the people above believed that Lin Bei would get the question right, even if he guessed blindly.

After all, the probability is really slim.

If everything is right, then Lin Bei doesn't need to study, he can just buy a lottery ticket.

however……

They didn't notice Zeng Xi, the school committee sitting in five rows and four seats, but his eyes suddenly lit up, and he tilted his head, looking at Lin Bei curiously.

At first, she was a little skeptical that Lin Bei's test paper was full of marks, whether there was really an element of plagiarism.

After all, although Lin Bei is talented in Chinese, mathematics is not Chinese, and it is very difficult to score from 0 to full.

But now, her doubt dissipated in an instant.

Don't ask why.

ask.

That is, Lin Bei's answer is correct.

Because she did it too.

Although her speed was a little faster than Lin Bei's, she was not much faster, almost front and rear.

At the same time.

Yu Huatian, the mathematics teacher on the podium, also tightened his eyes for a while, and his serious face was full of surprise.

However, he did not immediately admit the correctness of Lin Bei's answer, but instead asked, "Lin Bei, what's the process?"

【According to the title...】

[The two functions are symmetrical about y=x. 】

[It can be transformed from point A (x, y) to point B (y, x). 】

[It means that the original function y=2^x can be directly transformed into x=2^y, that is, y=log2x. 】

[Then f(x)=log2x, g(x)=log2x-x. 】

[Because it is established when x>0, -8 cannot be substituted directly, but it is an odd function. 】

【所以g(-8)=-g(8)=-[log2,8-8]=5，自然答案就是选项C了。】

Lin Bei didn't even go to the podium to use chalk to calculate, but stood still and talked for a while.

then.

There is no more.

Because the answer is already out.

But most of the students below, no matter how dazed their eyes were, they obviously didn't react.

As for Zhang San, Li Si, Wang Teng and Zhao Dali, they even exclaimed directly: "What are you talking about? Is it a scripture? Why can't we understand a single word?"

no doubt.

The four of them are real learners.

No matter how detailed Lin Bei's explanation was, to them, it was no different from the heavenly scriptures.

However, Yang Juntian, Lu Ren and Chu Bufan, the top academics, immediately changed their expressions.

Especially Yang Juntian.

There was a bad premonition in his heart.

just because...

He suddenly realized that Lin Bei might be right, because the process was very clear.

Although he is not very top-notch in mathematics, but his foundation is not bad, how can he not understand?

This is true.

After Lin Bei finished speaking.

Yu Huatian, the mathematics teacher on the stage, nodded again and again, and praised Lin Bei, "Well, logical thinking is very good, and the inverse function is used well. Let's look at the next question."

Ah!
Although not directly correct.

But the meaning is self-evident, Lin Bei is not only right, but also very good.

After all, you don’t even need chalk, and you can directly dictate to solve the problem. It’s not the 01:30 point that increases the difficulty.

If logical thinking is not strong enough, it is daydreaming.

See this scene.

Except that Zeng Xi didn't react much because she had expected it long ago.

The people below were so shocked that their eyeballs almost fell to the ground, "This...is it alright?"

But Zhang San Li Si Wang Teng Zhao Dali and the others were so excited that they almost slapped the table and shouted: "Dig the grass!"

However, I have little culture, and a word of digging grass is popular in the world.

Apart from this sentence, the four of them really couldn't think of any words to describe Lin Bei's astonishing move.

But on the other side.

Yang Juntian, Lu Ren, and Chu Bufan, these top academics, had very ugly expressions on their faces.

Especially Yang Juntian, instantly gloomy like water.

A small steel tooth made another "click", seemingly broken, but swallowed it without spitting it out.

have to say.

This is also a ruthless person!Hidden deeper than anyone else.

But Broken Steel Teeth is just the beginning.

The bigger shock seems to be yet to come.

only see...

【已知函数f(x)=6x^3+9x+1，若f(a)+f(a-1)＞2，则a的范围是（？？）】

This is the second question written by Yu Huatian on the blackboard. It is also a function, and you can fill in the blanks or choose.

However, this question is obviously more difficult than the first question.

Don't ask why.

ask.

That is the pitfall in the question.

The thinking of ordinary people is subconsciously substituting a and a-1 into the previous function to calculate the inequality.

But if you really want to do this, you will definitely fall into the trap.

Because once it is substituted into the solution, the final form of expression is so complicated that it makes people want to cry.

There are dozens of people in the class.

Apart from the fact that Zeng Xi's expression remained the same, but she only picked up a pen to write and draw quickly, obviously she had some ideas.

Everyone else frowned.

Including Yang Juntian, Lu Ren and Chu Bufan, they all felt the difficulty of this question.

Maybe.

It takes a lot of time to get it right.

But they didn't have time to write, and even the teacher Yu Huatian on the podium didn't write the options.

Lin Bei said directly, "Teacher, there is no need to write options. This question is not very difficult. It is nothing more than a problem of abstracting specific functions. There is no need to study the form of the function f(x), but only need to pay attention to its parity and monotony. sex."

"Among them, 6x^3 and 9x are both odd functions, but adding a constant 1 makes it not necessarily so."

"so……"

"The function can be deformed, and g(x) can be set."

“既g(x)=f(x)-1=6x^3+9x，为奇函数，且进行求导的话，g`(x)=18x^2+9＞0，说明这个函数一定是单调递增。”

"And the 1 on the right side of f(a)+f(a-2)>2 is very abrupt, and it is obviously not given for no reason."

"You can change the form."

"Split 2 into 1+1 and put it in front."

"Available……"

"f(a)-1+f(a-1)-1>0."

"Obviously it becomes g(a)+g(a-1)>0."

"That is, g(a)>-g(a-1)=g(1-a), because the function is monotonically increasing, so a>1-a."

"In the end, 2a > 1, a > 1/2."