Wanderer of the whirling world

Chapter 6 It's time to perform the real technique
Jia Zhiqing continued to bury her head in the calculations, and finally calculated the "five" in the ones place.

Just as he was about to write it down, the hand holding the charcoal pen paused slightly, and secretly glanced at Xin Ziqiu again. Seeing that he didn't respond, he wrote it down on the ground and started to calculate the next calculation problem.

This time it is more complicated, it is the root of the three times of 40, which is the fourth root.

Jia Zhiqing poured out more bamboo chips from the leather pouch and arranged them in rows.

She had just finished queuing, and Xin Ziqiu knew the answer before she could figure out the first place.

This time, Jia Zhiqing pondered for a long time, and she seemed to be struggling. She finally counted the first number "two", but she couldn't count any more, thin beads of sweat appeared on her white forehead.

The harder she tried to think, the more irritable she became.

At this time, a black cockroach crawled over the ground, Jia Zhiqing frowned, and popped out a counting chip, impartially, and firmly nailed the cockroach to the ground.

Xin Ziqiu was amazed by the precision of this hidden weapon.

Although he has studied martial arts since he was a child, he has never practiced hidden weapons, such as throwing knives and sleeve arrows, and he has only seen them in martial arts novels.

Now that she witnessed Jia Zhiqing's skill with her own eyes, she was filled with admiration.

At the same time, she secretly complained that this woman has such a temper, she couldn't figure out the problem by herself, but she vented her anger on bugs.

In order to avoid accidental injury, he simply muttered in a low voice:
"250 two."

After hearing this, Jia Zhiqing raised her head immediately, her black eyes burst into light, she looked at Xin Ziqiu with an expression of disbelief on her face.

She bowed her head to check.

Checking the calculation is much easier than solving it. After about a cup of tea, she finally confirmed the result of 250 two. She was taken aback, looked up at Xin Ziqiu and said:
"You know how to calculate? You don't need to count, how did you calculate it? It's so fast?"

Xin Ziqiu didn't know how to explain it, did he explain the decomposed prime factor to the ancients?Where can they understand.

Moreover, he took advantage of these two questions. If the original number cannot be found as an integer square root, or if it has a particularly large prime factor, it cannot be calculated so quickly.

After all, he is just a top student with a superior IQ, not a human computer.

So he laughed dryly twice, and said in a secretive way:
"This... I know a thing or two, but my calculation is different from ordinary people's. I have my own school, and I can't explain it clearly in a few words."

It's just that the more perfunctory he speaks, the more inscrutable and unpredictable he becomes.

On the side, Jia Xian saw all this in his eyes, and was also very surprised to see that Xin Ziqiu solved the two calculation problems of finding the square without any effort.

Just as Xin Ziqiu guessed, he was the famous mathematician Jia Xian himself.

Jia Xian's official career was not going well. When he was young, he served as Zuoban Dianzhi in the court, but he was just an ordinary military officer of the ninth rank.

The Song Dynasty emphasized culture over military affairs, and even the famous Yang family of Tianbo Mansion and the famous general Di Qing were squeezed out, not to mention Zuo Ban Dianzhi, a small official with the size of a sesame mung bean.

However, it was a blessing in disguise. It was precisely because of poor official luck and idleness in official duties that Jia Xian had a lot of time to study mathematics and achieved achievements that are famous in history.

At this time, in his opinion, although the method of prescribing the prescription is not a difficult problem, it is just a game for him and his granddaughter to pass the time. To get the answer, this ability is really unheard of and unprecedented.

He wanted to ask, but before he could say anything, his granddaughter Jia Zhiqing cupped her fists at Xin Ziqiu and said seriously:

"It turned out that the little girl didn't know Taishan with her eyes. I didn't expect that the brothers of the Xin family would break new ground in the study of alchemy and mathematics. May I ask which master you studied under?"

Seeing that Xin Ziqiu was young but proficient in arithmetic, she guessed that he must be the proud student of a master of arithmetic.

Xin Ziqiu was momentarily at a loss for words, so how could he answer.

Let's say there is no master. At such a young age, it seems too abrupt and a bit unbelievable.

Just make up a master, I don't know how to tell this nonsense.

He thought for a while, took a compromise and replied:
"My master's surname is Zhang Mingkun. He doesn't like to be lively and has lived in seclusion for many years."

He is the worst at lying, but this sentence is not a lie.

When he was doing research at Yanda Mathematics Institute, his mentor was Zhang Kun, who was also a well-known expert in number theory in China.

The old man has a withdrawn personality and has no family. He lives in the dormitories of several courtyards. He even leaves Yanyuan only a handful of times throughout the year. It is not a lie to say that he lives in seclusion.

Jia Zhiqing had never heard of Zhang Kun's name, so she turned to look at her grandfather.

Jia Xian shook his head, this name was also very unfamiliar to him.

He has heard of all the mathematicians in the world, but he can't figure out who this Zhang Kun is.

Of course, even if he wanted to break his head, he would never guess that the young man beside him and the Zhang Kun he was talking about were not from this generation at all.

Jia Zhiqing loves to be competitive the most. She has studied arithmetic with her grandfather since she was a child. Although she is young, she thinks she has acquired most of her grandfather's true teachings and has unique attainments.

Today, she was at a disadvantage in front of Xin Ziqiu, who was similar in age, so she naturally refused to let it go.

So he gritted his teeth and said:

"It's rare that the brothers of the Xin family are also proficient in spells. We have nothing to do in this barren village, so how about we learn from each other?"

As he spoke, he took out a short knife from his pocket, and suddenly a cold light radiated from it, as if a blazing lightning had struck in the ruined temple.

Xin Ziqiu was startled and almost jumped up.

This girl is so delicate and beautiful, why is she so angry?Unexpectedly, if they disagree with each other, they will draw their swords and fight desperately.

Were all ancient people so angry?
As soon as he changed his mind, he saw Jia Zhiqing cut two cockroaches crawling back and forth on the ground into four pieces with a flick of the dagger.

Immediately after scribbling on the ground, he actually wrote a calculation problem.

Xin Ziqiu pressed his chest, it turned out that he had frightened himself.

It's no wonder, being dragged into a new world inexplicably, and having just fought a battle with Gu zombies, anyone would be a little nervous.

He looked down at the calculation problem, and it turned out to be a "square stack counting problem".

"There are piles of fresh fruits today, there are fourteen below, how many?"

The general idea is to arrange each layer of fruit into a square, stacked into a square stack, the top one, the bottom 2 times 2 is four, and the bottom 3 times 3 is nine, and so on, the bottom is 14 times 14, Ask how many fruits there are in total.

Translated into modern mathematics, it is to find the sum of squares from 1 to 14.

Most of the mathematics in ancient China started from reality, and they were real problems encountered by the people in labor and engineering.

For example, this counting question to find the sum of squares was born out of the practical problems that fruit vendors in the vegetable market would encounter, and it is very down-to-earth.

In fact, the problem of finding the sum of squares is only one of the summation of series in modern mathematics. Even in ancient times, there were different series of summation problems such as square stack, triangular stack, and small stack.

Shen Kuo, another great mathematician in the Northern Song Dynasty, who wrote "Mengxi Bi Tan", made outstanding contributions in this regard.

The summation method of stack accumulation technique he invented, also known as the gap accumulation technique, gave several formulas for the summation of series. This achievement comes from the chapter "Technology" in "Mengxi Bi Tan".

And "Mengxi Bi Tan" is a comprehensive notebook work, discussing mostly various phenomena in the daily production and life of that period, including many mathematical problems in engineering and machinery.

It can be seen that as early as the Northern Song Dynasty thousands of years ago, the Chinese had already skillfully applied mathematics to solve many practical problems in daily production and life.

This is centuries earlier than the West.

Xin Ziqiu smiled. He hadn't done this kind of elementary math problem for a long time, and he had forgotten the summation formula of the sum of squares.

However, he doesn't need to memorize these formulas by rote, he can use several methods to derive them casually.

After thinking for a while, he replied:

"One thousand and fifteen."

(End of this chapter)