Xueba, I beg you to go and escort him quickly!

He's a bit overwhelmed.

"I think the math finale that is easy to test is deliberately set to be so difficult."

Xu Heng smiled, "It's like this, don't you know?"

Yang Kaixuan was speechless, and didn't know what to say for a while.

Xu Heng, "Show me the title."

He also wanted to see what the question was, which stumped the former No. [-] student in the whole grade!

topic:

已知函数f（x）=（1/根号下（1+x））+（1/根号下（1+a））+根号下（ax/（ax+8））

(1) When a=8, find the monotone interval of f(x);

(2) For any positive number a, prove: 1<f(x)<2.

Xu Heng knew this question.

This is the average score for the province that year.

None of the 30 candidates in the province got it right.

And the highest score is 9 points and there is only one person, and 8 points have two.

After reading the answers, the examinees didn't even have the idea of ​​copying!

It's so hard!

too complicated!

PS: Thank you [tail number 3992] [tail number 0732] for your support!

Kneel for all support!Explosion continues! .

Chapter 129

A class is divided into top students and bad students.

And among the top scholars, there will be three, six, and nine grades!

Yang Kaixuan is regarded as the best student in the same grade!

But the gap between him and Xu Heng is even bigger than the gap between the bottom one in the school and him!

Yang Kaixuan looked at Xu Heng, and Xu Heng looked at the question.

Yang Kaixuan, "When I read the answer, I feel a little headache. Xu Heng, why don't you give it a try?"

Xu Heng said, "Where did you find these old-fashioned topics?"

He kept looking down at the test paper without looking at Yang Kaixuan.

Antique?

Old antique topic?

Yang Kaixuan was speechless, and didn't know what to say for a while.

"I have done all the college entrance examination questions in recent years, and I think the difficulty is not interesting, so I found some more difficult ones."

More difficult!

This is the truth of Yang Kaixuan.

This question is indeed a bit difficult for a former first grader.

Several other people in the dormitory felt even more stressed.

All of them have big heads.

"If Yang Kaixuan didn't look at the answer, he wouldn't be able to answer this question."

"Hey! It's amazing that he can understand the answer, okay! I think the answer is foggy!"

"Tell me, will Xu Heng know?"

"Yang Kaixuan, don't stump Xu Heng with this question!"

Yang Kaixuan shrugged, "I think so too, but judging from Xu Heng's attitude just now, this question is like Zhang Fei eating bean sprouts, a piece of cake for him."

The other four roommates expressed doubts.

Everyone also looked at Xu Heng.

Xu Heng raised his head after a while and looked at Yang Kaixuan, "Although this question is difficult, there are four or five ways to solve it."

"The interval of the first question, you can understand it by reading the answer!"

Yang Kaixuan was stunned, "What! What... what did you just say?"

"???"

Xu Heng said calmly, "I ask you the first question, do you understand?"

Yang Kaixuan nodded, but immediately shook his head again, "It's not this sentence, it's the last sentence!"

Xu Heng frowned, "I said four or five solutions?"

Yang Kaixuan's eyes were about to pop out, "Four or five?! Four or five solutions? This, this, this...?"

The other four roommates were also stunned on the spot, they looked at each other in blank dismay.

"Four or five? Four or five! How is that possible! Did you hear wrong?"

"Xu Heng, are you sure?"

Xu Heng waved his hand, "Why do you look so rare and strange!"

Fuss?

Of the 30 candidates for this question, only one scored 9 points!Two scored 8 points!

Average score!

This is a finale big question!

Why in your mouth, it's really as simple as one plus one equals two!

!!!

Everyone's scalps were numb and they came together!

Xu Heng looked at the five people, "Which one do you want to listen to..."

But as soon as he finished speaking, Xu Heng sighed, "Let's talk about it!"

Several people echoed, "Okay!"

Xu Heng spoke directly to the proof of the second question.

"Let b=x, c=8/ax, then question (2) is equivalent to..."

"..."

"The inequality obtained is somewhat similar to the last question of the Western Olympics a few years earlier."

Western Olympics?

Yang Kaixuan and the others were dumbfounded.

How big is Xu Heng's question bank? !

"In addition, there are similar topics in CMOs."

puff...

There are similar?

Are we ignorant?

While talking, Xu Heng wrote down the related inequalities.

"In this case, it can be proved!"

The first method was said by Xu Heng, and ended hastily.

Yang Kaixuan and the others opened their mouths wide and were speechless for a moment.

Xu Heng, "Hey! Wake up, hey? Do you understand?"

Yang Kaixuan and the others shook their heads collectively.

"Forehead……"

Xu Heng really separated them from Yue Pingting, Xu Heng thought they should be much better than Yue Pingting.

They should belong to the type that knows everything!

But Xu Heng overestimated them!

Even Yang Kaixuan said, "Xu Heng, are you overestimating us? I think this method is more difficult than the problem!"

Others echoed, "I can't even understand the question, and we can't even understand your answer!"

Xu Heng, "Uh...｀々..."

I thought you could do it!

But Yang Kaixuan and the others shook their heads collectively, no, no, no, we can't!Please let me go!We are just ordinary students!

Also please don't be treated specially!

the first time!

Yang Kaixuan and the others felt the disadvantages of being a top student.

"Hey...Xu Heng, you should find a simpler way to talk about it!"

Yang Kaixuan frowned.

Xu Heng, "Okay...give me a scrap of paper and a pen."

Using it as straw paper, Xu Heng began to answer with his own thoughts.

solution:

For any given a>0, x>0, because...

……

First prove that (x) > 1.

because……

……

The inequalities in the process are listed like building a building!

Xu Heng's writing is like a waterfall, so cool!

But Yang Kaixuan and the other five were even more dumbfounded!

Xu Heng wrote so fast that they couldn't even keep up!

"I'll go! What is this and what? This step requires six or seven inequalities?"

"Damn! There's more!"

"I'll go! I'm a scumbag, I'm definitely a scumbag!"

These few are the top ten and top twenty existences in the grade!

Mathematics scores are among the best!

But looking at the proof process written by Xu Heng, they are willing to be scumbags.

"too difficult!"

许衡，“此时，f（x）=1/（根号下（1+x）+1/（根号下（1+a）+1/（根号下（1+b）＜2……”

The inequality that Xiang Xu Heng just mentioned can be seen everywhere!