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

"Then you accompany me home to get clothes..."

This is to unlock a new suit!

Xu Heng was full of expectations.

……

These two days are fleeting.

After Xu Heng returned to school, he continued to give Yue Pingting papers, all kinds of targets.

Yue Pingting became more and more confident!

Doing test papers is becoming more and more confident.

Until she started to take the initiative to hand in the papers in advance.

"Look at it!"

It's a math test paper.

Xu Heng took a general look, and after picking out a few mistakes, he focused on the last question.

It is known that the function f(x)=x3+ax2+bx+1 (a>0, b∈R) has an extreme value, and the extreme point of the derivative function f(x) is the zero point of f(x). (Extreme point refers to the value of the corresponding independent variable when the function takes the extreme value)

(1) Find the functional relational expression of b with respect to a, and write out the domain of definition;

(2) Proof: b23a;

(3) If f(x), f'(x), the sum of all extreme values ​​of these two functions is not less than 7-2, find the value range of a.

Yue Pingting got the first two questions right, and she got the third question right, but she got it wrong.

Not only was the final answer wrong, but her train of thought was also wrong.

Xu Heng, "This question tests the use of derivatives to study the monotonicity, extremum and zero points of elementary functions, and tests the comprehensive use of mathematical thinking methods to analyze and solve problems and the ability of logical reasoning."

Before giving the lecture, Xu Heng first responded to Yue Pingting to determine the nature of the topic.

"Let's mainly look at the third question."

“从第一问我们可以知道，f（x）的极限点是x1，x2，而且x1+x2=(-2/3)a,x12+x22=（4a2-6b）/9。”

Yue Pingting listened carefully and nodded.

Xu Heng continued, "Thus f(x1)+f(x2)..."

Only halfway through, Yue Pingting immediately understood.

"Wait! Wait! Stop talking, let me do the math!"

"Hold on……"

Yue Pingting took back the test paper and rushed to answer the questions by herself.

"..."

"Remember f(x), the sum of all extreme values ​​of f(x) is..."

"Because... monotonically decreasing..."

"..."

"Therefore, the value range of a should be (3,6]!"

"Xu Heng, am I right?"

Xu Heng nodded, "That's right."

Yue Pingting was also overjoyed!

"Then I'll wait for you, you can ask me a few more questions!"

Because the end of the semester is approaching, all the courses to be studied have been completed, and they are basically self-study courses.

Everyone is checking for leaks.

This gave Yue Pingting time to do more of Xu Heng's test papers.

one copy!two copies!three servings! ...

math!physics!Chemical! ...

Do the questions differently every day, if you don't know it, Xu Heng will talk!

After the lecture, Yue Pingting understood, and Xu Heng tore it up.

In this way, I have been insisting until the day before the final exam.

this day.

It was snowing heavily outside.

Xu Heng watched everyone excitedly looking forward to the final exam, all kinds of preparations!

Admission ticket...exam room...

All kinds of busy work!

On the contrary, Xu Heng could only look at the heavy snow outside the window, feeling a little melancholy.

At this time, the principal sent a message, "Xu Heng, there has been snow these two days, and it's colder on rainy days. Come to my office, let's drink tea and play chess together!"

Xu Heng is gone!

Just when the students were taking their final exams, Xu Heng was sitting in the principal's office, in the air-conditioned room, drinking tea, playing chess, and watching the snowflakes falling slowly outside the window.

Cozy...

Suddenly, Xu Heng felt that it was really cool not to have to take the final exam!

"Student Xu Heng, you're in a trance again..."

Xu Heng smiled, "Principal, I'm a general, it's because you're not concentrating!"

Principal, "*%￥#￥￥￥..."

He never expected that Xu Heng's chess skills are so high.

The principal played three games in a row and lost all of them.

"Hiss... I'll come back to ask you for advice when I become more diligent!"

Don't play chess?

Why?

Xu Heng aimed at the computer on the principal's desk.

Xu Heng, "Principal, can I use your computer?"

Principal, "Yes..."

Xu Heng smiled, a little badly.

headmaster,"???"

Xu Heng, "Principal, how is the Internet speed in your office?"

Principal, "It's okay, so you want to...?"

Xu Heng, "Download a game, can you?"

May I?

Xu Heng has already asked this question, can you say no?

The principal's eyes twitched, "Uh...you download it! Just download it! But keep a low profile!"

The principal is extremely humble.

Xu Heng, "Understood! Thank you, principal..."

The point is that I don't want to download the game either!

But who made your chess skills so bad...

PS: Thank you [tail number 5960] for your support!

There is support behind!I pray for everything this time! .

Chapter 226

"Principal! Your internet speed is good! Downloads are all 20 or 30M!"

The principal watched Xu Heng download LOL from the official website to his computer.

What can he say?

I can only squeeze out a smile that is uglier than crying, and nod, "Mmmmmmm!"

game download!

Unzip!

Sign in!

It doesn't take much time.

After Xu Heng got on the number, he didn't hesitate much, so he queued up alone.

Just loaded the game.

Xu Heng asked, "Principal, do you have headphones?"

The principal immediately shook his head.

"Uh... ok ok, forget it if you don't have one."

Games start.

Xu Heng is playing blind.

Because of the mouse and keyboard, his operation is a little rusty.

Several times escaped under the siege of the enemy.

The headmaster looked shocked.

But as Xu Heng became familiar with the keyboard, it was time for the show to operate.

Double kill!

Three kills!

With the cooperation of his teammates, Xu Heng also scored four kills!

Although the headmaster didn't understand the game very well, Xu Heng killed so many people in the area, which is amazing!

Unable to bear it, the principal gasped.

game over!

Xu Hengfang won!

Xu Heng looked at the time, the Chinese exam was just halfway through.

Xu Heng started another game.

The principal stood by and watched.

Another thrilling round.

The teammate was killed, and the other five besieged Xu Heng.

The teammate held back the opponent and let Xu Heng go, but instead of leaving, Xu Heng made a sharp maneuver and killed the five opponents!

Four teammates who are already dead, crazily buckle 6!

Even the opponent on the opposite side also got up to 6.

9 people except Xu Heng, collectively!

The headmaster muttered, "6..."