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

Xu Yueshan frowned, he hadn't gotten to the point, "So... the teacher made a mistake in grading the test paper?"

Xu Yuehai's face turned dark, "*%￥#@#￥......"

Makes no sense!

It doesn't make sense at all!

Anyway, after the meal, Xu Yuehai stared at Xu Heng the whole time.

Like looking at a monster!

"Xu Heng, how did you learn it!"

Just after asking, Xu Yuehai seemed to slap himself a big mouth.

What did Xu Heng learn and how did he learn it?

Everyone has learned enough, go to class and sleep every day...

Looking at his son, Xu Yuehai, he sighed resentfully.

No comparison, no harm!

"You should learn more from your brother!"

After finishing speaking, Xu Yuehai regretted it again.

Because Xu Heng had dinner, he went to the e-sports room and played games again.

Xu Zongyun pouted and asked Xu Yuehai, "Dad, so I went too?"

Xu Yuehai stared, "How dare you! Learn from me! Go!"

Xu Zongyun was helpless, "Didn't you let my brother and I learn it?"

Xu Yuehai, "Hey! You're still kicking your nose, aren't you? Go! Don't you know how much you weigh?"

Xu Zongyun shrugged, "Okay...!"

Before the holiday, Xu Yuehai prepared a lot of materials and test papers for Xu Zongyun.

It was because he was afraid that he would be left too far behind by his classmates after a winter vacation!

According to Xu Yuehai's understanding, many people will secretly give their children tutoring during the holidays, fearing that they will relax and fail to keep up with their studies.

Xu Yuehai took great pains.

Xu Yueshan and Zhou Xiu'e looked at the materials and test papers that Xu Yuehai took from the car for Xu Zongyun, pile after pile!

They are all distressed.

Zhou Xiu'e sighed, looked at Wei Xiaojiao, "You don't care!"

Wei Xiaojiao, "Sister-in-law! This is something Zong Yun must learn!"

Zhou Xiu'e, "How can he finish his studies! It's a rare winter vacation, and you don't give him a chance to have fun."

Wei Xiaojiao, "Sister-in-law! You can't play! If he is like Xu Heng, we will let him play! But he is not!"

With that said, Wei Xiaojiao raised her head subconsciously.

So is Zhou Xiu'e.

The gap between the two brothers is really too big.

One had a great time playing in the e-sports room, and the other studied hard.

The difference!

At this time, in the e-sports room.

Yue Pingting asked, "What fruit do you want to eat? I'll wash it for you!"

Xu Heng, "Grapes."

Yue Pingting blushed instantly!

Xu Heng, "Uh...don't make trouble! I really want to eat."

Yue Pingting lowered her head and ran away silently.

Xu Heng, "%￥####..."

"Don't go! You have to trust me!"

Xu Heng believed that Yue Pingting must have deliberately refused to wash herself and ran away with an excuse.

This round of the game is over, Xu Heng went to wash by himself.

Passing by the bedroom, Yue Pingting rolled her eyes at Xu Heng, "Smelly pomegranate!"

Xu Heng stared, "!!!"

"You girl! I always feel that your ulterior motives are not in drinking!"

"Tell me the truth... Did you do it on purpose!"

"If it's not true, I can't be wronged by you!"

With that said, Xu Heng locked the bedroom door behind his back.

click!

Yue Pingting was instantly excited, "You, you, you... Xu Heng, what are you doing! Don't make trouble!"

Can!

It's too late!

Xu Zongyun, who came up from the first floor, was holding the test paper and was going to ask Xu Heng questions, but the e-sports room was found, but there was no one, and the study room was found, but there was no one.

"Are you taking a nap?"

"Forget it...let's wait and come again."

Moreover, Xu Zongyun vaguely heard some strange voices.

But he didn't think much of it, and went downstairs.

About an hour later, Xu Heng came out of the bedroom.

"Huh!"

Xu Heng heaved a long sigh, and his voice was not small.

Xu Zongyun heard Xu Heng's voice, and then ran upstairs.

"Brother! Did you nap for so long?"

Nap... so long?

Xu Heng rolled his eyes at Xu Zongyun...

Meaningful.

Xu Zongyun, "???"

Xu Heng, "What's the matter?"

Xu Zongyun, "Brother! Please read a question for me!"

Pass the test paper to Xu Heng.

Xu Heng walked into the study with the test paper, followed by Xu Zongyun.

After taking these few steps, Xu Heng finished reading the questions and thought about how to solve the questions.

As soon as you sit down, "I'll tell you one by one the three solutions to this question!"

Xu Zongyun opened his mouth wide on the spot.

"No... no, no, no! Brother! Are you serious? You knew the answer as soon as you saw the question? Do you have a different way of solving the problem?"

· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·??????????????

Xu Heng looked at the shocked Xu Zongyun and nodded seriously.

Xu Zongyun, "%￥%#@#￥￥!!!"

Xu Heng, "Don't make a fuss, just read the questions."

topic:

Note U={1,2,...,100}, logarithmic sequence {an}(n∈N*) and subset T of U, if T=Φ, define ST=0; if T={t1, t2,... , tk}, define ST=at1+at2+...+atk.For example: when T={1,3,66}, ST=a1+a3+a66.Let {an} (n∈N*) be a geometric sequence with a total ratio of 3, and when T={2, 4}, ST=30.

(1) Find the general term formula of the sequence {an};

(2) For any positive integer k (1≤k≤100), if T{1,2,...,k}, verify: ST<a(k+1);

(3) Set CU, DU, SCSD, and prove that SC+S(CnD)≥2SD.

Xu Heng, "This question mainly examines basic knowledge such as general term formulas and summations of geometric series, and examines the ability of algebraic reasoning, transformation and naturalization, and comprehensive use of mathematical knowledge to explore and solve problems."

"You have to be clear about this!"

Xu Zongyun was still in shock, but Xu Heng had already started.

Xu Zongyun, "!!!"

"Wait! Brother! Let me get back to my thoughts a little bit!"

"call……"

After a few seconds of delay, Xu Zongyun said to Xu Heng, "Okay! It's done! Brother!"

Xu Heng, "Look at the first question first. Here, we can get an=a1*3[(n-1) power], n∈N*, so when t={2,4}, Sr+..."

0  …  

"So, the general term formula of the sequence {an} is an=3[(n-1)th power], n∈N*."

"Look at the second question!"

"Because T{1,2,...,k}, an=3[(n-1) power]>0, n∈N*..."

"So, it's very simple, right?"

"The following is the last question."

"There are three cases to be distinguished: if D is a subset of C, if C is a subset of D, if D is not a subset of C,..."

"..."

"Assume that k is the largest number in E, and l is the largest number in F, then k≥1, l≥1, cut k≠l..."

……

"So, SC+S (CnD) ≥ 2SD+1, and in the end, SC+S (CnD) ≥ 2SD."

"do you understand?"

"Let's talk about the second problem-solving idea..."

Xu Zongyun was stunned for a while, "Wait! Brother! Let me digest it! Let me clear it up! You speak too fast! I can't keep up with my thoughts!"

Xu Heng spoke very quickly when he gave lectures to anyone. He felt that lectures were a waste of time.

Of course, except for Yue Pingting.

This is his woman, if I don't love her, how can I do that!

Xu Heng, "Then you digest it first, I'm going to play chess next door, after you digest it, come to me, and I will tell you the second method."

Xu Zongyun suddenly felt helpless, "Okay, okay..."

Xu Heng got up and went to the e-sports room, leaving Xu Zongyun stuck in the study for this question.

His scalp was numb, "My brother must have spoken too fast!"

After that, I buried my head and sorted it out carefully.

This sorting out took more than ten, twenty, and ten minutes to pass.

Xu Heng's first round was almost over, so Xu Zongyun came here.

"Let's look at the first question first..."

Xu Heng was talking while playing.