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

The flags are one after the other.

I have to say that everyone present is ruthless, and it seems that they are going to fight Lin Bei today.

Not only those who were jealous of Lin Bei before, but also many people who watched the fire from the other side got involved.

Neither hatred nor hatred.

But purely watching the excitement is not a big deal.

of course.

The ones who clamored the most were Yang Juntian and others, who kept making waves and fanning the flames.

Don't ask why.

ask.

Just now, Lin Bei had answered two questions in a row, causing them to be slapped in the face one after another, and they were completely mad with anger.

Especially Yang Juntian.

How much he wanted to see Lin Bei suffer a setback!

So he stands the most flags and is the most ruthless. He is too weak to wash his hair while standing on his head, so he just stands on his head and has diarrhea.

It's not that he wants to cheat food and drink, but this time he has enough confidence that Lin Bei will definitely not be able to solve this problem.

after all.

This question is really difficult.

It's okay if he doesn't have any ideas.

He also whispered to Lu Ren, the math class representative, and Chu Bufan, the monitor, who were next to him.

turn out……

Regardless of whether it was Lu Ren or Chu Bufan, they all shook their heads for a while, sighing secretly that this question is not easy to solve.

Although the title is simple.

But if you really want to calculate it, it is not so complicated, and it takes a lot of time to deduce it slowly.

Perhaps the entire class, only the school committee member Zeng Xi can handle it well, and it is estimated that it is impossible for the others.

As for Lin Bei, it is even more impossible.

Even if Lin Bei got two questions right, he would definitely not be able to answer the third question.

Unless Lin Bei's mathematical strength can surpass him, Lu Ren, Chu Bufan and others can catch up with Zeng Xi's height.

Gee!

Zeng Xi is the top student in the class!
In the whole school, they are well-known, and their grade ranking is firmly in the top [-], and they can even enter the top ten.

Among the girls, their strength is second only to the school girl Zhao Qinghan, and the bullfrogs can be described as a batch, and they can be called the pride of heaven.

Although Lin Bei is now closer to Zeng Xi.

But being close doesn't mean that Lin Bei's strength is as strong as Zeng Xi's, okay?

But next second.

Yang Juntian was about to vomit blood again.

only see...

Mathematics teacher Yu Huatian smiled meaningfully after finishing writing the question, and handed over the chalk, "Come on, student Lin Bei, here is the chalk, come up and solve it!"

"This question is a solution question. It is slightly more difficult than the previous two questions. It may not be easy to solve it."

"so……"

"I'll give you 15 minutes, and you can freely explain and see how much you can write."

"You don't need to force it too much. After all, you have already done two questions and proved your strength."

"This time the test paper has a perfect score. The teacher believes that you did it yourself. I apologize to you for the previous mistrust."

have to say.

Mathematics teacher Yu Huatian is still able to deal with it. After realizing his mistake, he apologized to Lin Bei in public.

That attitude is also a good group.

But an apology is an apology.

This is also to earn some face back.

Although he said that the above question was only a little difficult, you could tell from his tone that he was humbled.

Actually.

He thought that Lin Bei would definitely not be able to solve this problem.

After all, it is true that it is also the finale of the derivative, but the difficulty is also divided into grades.

If the difficulty of the derivative finale of the previous test papers was divided into second and third grades, then this one is fifth and sixth grades.

This difficulty has more than doubled directly.

That's why.

He only gave Lin Bei 15 minutes to say nothing, and told him not to force him too much, but to write as much as he could.

however……

hear him.

Lin Bei didn't accept the chalk stub that was handed over, but only thought for a while, then waved his hand and shook his head, "Teacher, this question is indeed a little difficult, but it's okay."

"There is no need for chalk, I'll just dictate directly! This will save a lot of time."

Gee!

Lin Bei really couldn't stop talking.

Obviously Yu Huatian gave him chalk and let him think about it slowly, but in the end he had chalk and didn't use it.

even.

He still wants to save time?
But the more amazing thing is yet to come.

As soon as Lin Bei finished speaking, he immediately said, "Well, there seem to be two solutions to this question."

"One of them is to use the knowledge of sub-parameter + isomorphism + exponential tangent scaling + hidden zero point to solve it."

“题干为x(e^x-a)-2lnx+2ln2-2≥0，很明显这是在x＞0时的成立。”

“先乘开分参，变成xe^x-2lnx+2ln2-2≥ax，x＞0。”

“则a≤(xe^x-2lnx+2ln2-2)/x，x＞0。”

“令g(x)=(xe^x-2lnx+2ln2-2)/x，x＞0。”

"One more isomorphism."

"Then g(x)=(e^(x+lnx)-2lnx+2ln2-2)/x."

“再右边分子分母同除一个2,得g(x)=(e^(x+lnx-ln2)-lnx+ln2-1)/(x/2)=(e^(x+lnx-ln2)-(x+lnx-ln2)-1+x)/(x/2)。”

"According to linear scaling..."

"f(x)=e^xx-1≥0, this function is always established, and the equal sign is taken if and only when x=0."

"so……"

“g(x)=(f(x+lnx-ln2)+x)/(x/2)≥(0+x)/(x/2)=2。”

"Then verify the access conditions."

"Let h(x)=x+lnx-ln2, x>0."

“h`(x)=1+1/x＞0，对x＞0恒成立，即h(x)在(1,+∞)为单调递增。”

"And h(1)=1-ln2>0."

“h(1/2)=1/2-2ln2＜0。”

“根据零点存在性定理，这中间肯定存在唯一的x0属于(1/2,1)使得h(x0)=0。”

"That is x0+lnx0-ln2=0."

"So when x=x0, wait."

"So g(x)min=g(x0)=2."

"So a ≤ 2."

"So the value range of a is (-∞, 2]."

Ah!
That's it for the first method.

It seems to be both complicated and simple, as long as you master the knowledge of sub-parameters, isomorphism, tangent scaling and hidden zero point, you only need to solve it step by step.

but……

Many people present, including Yang Juntian, just stared wide-eyed, with a confused look on their faces: "???"

【Kids, do you have a lot of question marks? 】

Using this sentence to describe the expressions of Yang Juntian and others at this moment, it could not be more accurate.

It is really……

They were all shocked by Lin Bei!

Even petrified.

Such a difficult derivative question, but Lin Bei didn't even use chalk, but directly dictated the solution?
Suddenly, the class was extremely quiet.

He didn't even dare to breathe, he just kept swallowing in his throat.

And turned his attention to the mathematics teacher Yu Huatian on the podium, wondering if Lin Bei had the right solution.

But Yu Huatian didn't speak yet.

Lin Bei continued: "The second method is to use isomorphism + exponential tangent scaling + hidden zero point."

"If you don't use subparameters, it's a little more complicated."

"That is……"

"xe^x-ax-2lnx+2ln2-2≥0。”

“e^(x+lnx)-2lnx+2ln2-2-ax≥0。”

“e^(x+lnx-ln2)-(x+lnx-ln2)-1+(1-a/2)x≥0。”

"Let g(x)=e^xx-1..."

"...(process omitted)..."

"So the value range of a is (-∞, 2], which is the same as the conclusion of the first method."