At night, on Chixia Mountain, in the reception room that used to belong to Christina, the fireplace was blazing.

Compared with the magic array, this primitive heating method can create a special and indescribable sense of security and comfort in winter nights.

Una brought two cups of hot tea and quietly withdrew.

"Tell me, boy, how did you discover that conjecture?" said Grantis, as kind and casual as an old friend.

"Didn't Master Kraft tell you? I have amnesia...... Donner said, embarrassed.

"I know, but if you remember that conjecture, you may remember how you found it. Come on...... Maybe it will help you regain your memory......" Grantis encouraged.

"Hmm...... I do remember some ......" Donner didn't know how Fermat came up with that conjecture, and he had to look for a possible logic in his math maze: "Originally, I probably just wanted to use a ruler to solve the problem of fusing two cubes. ”

Donner is talking about one of the three great geometric puzzles of ancient Greece, a variant of cubic multiplication.

"Trust me, kid, you can't do that. Grantis said confidently as he cupped his cup in both hands, took a sip of hot tea.

Donner nodded, of course this can't be done, the three major geometric problems of ancient Greece are unsolvable.

"Yes, then I stumbled upon the fact that any cube with two integer side lengths, if they are fused into a cube, the side lengths are not integers...... I've tried countless times but it didn't work. Donner described as he gathered his thoughts.

"And then you found out that this law exists above the third dimension?" asked Grantis.

"Exactly. ”

"Extrapolating number theory conjectures from geometric problems is beautiful!" Grantis exclaimed, "John, you have a mind fit for the study of mathematics." ”

Donner smiled modestly and took a sip from his cup, which was supposed to be a fruit tea made by Una herself, and she had a pair of skillful hands.

"So, geometry or number theory, which is the one that interests you the most?" asked Grantis.

"Hmm...... Number theory......" Downer mused, not really good at or liking number theory, but because the foundation of number theory in this world is much more backward than geometry, and it is more suitable for him to play.

"Tell me, what else have you found interesting?" asked Grantis with interest.

"Hmm...... I only remember one way of proving whether the number of prime numbers is infinite or not. "As for the ready-made proof of number theory, Donner really only remembers this one.

"Oh...... Tell me, is it the same as I thought......"

"Yes, if the number of primes is finite, then multiplying the finite number of primes and adding one, if the number obtained is prime, it naturally overturns the previous assumption, and if the number is a composite number, then its factor is obviously not any of the finite primes in the set just now......"

The corners of Grantis's mouth gradually curled as Donner's narration began.

"That's it," he said with a smile, "it's the simplest and most perfect way to prove it." ”

Donner also laughed with him, but he was thinking in his heart, it seems that he can't impress the other party with this little trick, and he must come up with some big killing weapons.

Thinking of this, he slowly stood up: "My lord, I also found a very fun game. ”

"Oh, what game, is it also about math?" asked Grantis.

"I don't know if it matters," Donner replied, "It's kind of like a geometry problem, but it's not quite." ”

Donner walked out the door, called for Una, and whispered a few words. It didn't take long for Una to bring him a stack of blank paper and a few drawing pens, as well as five bottles of magical metal.

"My lord, this game is like this," Donner said as he drew on the white paper, and after a while, he handed the finished paper to Grantis, "If this is a map and you need to color each jurisdiction in different colors, you can be confident that you can use at least a few colors, provided that each adjacent jurisdiction can be marked with a different color." ”

Grantis looked at the map in his hand, and after a moment of silence, he said, "Six?"

"My lord, I can do this with four colors, can you believe it?"

Grantis glanced at Donner suspiciously and shook his head slightly.

After a few minutes, Grantis looked at the map in front of him that was painted with four series of magical metal.

Sure enough, each jurisdiction was painted a different color, and each neighboring jurisdiction was never duplicated.

"Your map is too simple...... Grantis frowned.

Downer handed out a blank piece of paper: "You can design a map, as complex as you want." ”

......

An hour later, Grantis was defeated, and no matter how complex the map he designed, Donner could use four types of magic gold to distinguish the different districts.

Obviously, Donner is just playing tricks and borrowing this game to show Grantis the four-color theorem.

"Your Excellency...... Is this mathematics?" he asked, deliberately puzzled—of course it was a mathematical problem, a branch of geometry, topology.

"Well......" Grantis muttered for a long time, "it's a math problem!" he finally concluded.

Then, Grantis looked up at Donner seriously, "John, would you like to come to the Superintendent's Academy?" and be my assistant!"

At this moment, Donner felt a little trance, as if he had returned to the island of Lante four years ago, when Professor Victor asked Donner the same thing.

This time, though, the situation is completely different.

Downer was no longer the pauper kid on the island of Lante, a position of assistant to the president of the Governor's Society, and there was no appeal to him.

He showed this in front of Grantis, just to get the other party's attention, and then impress Kraft to make him willing to marry Shaida to him.

So, Donner looked embarrassed and shook his head slightly.

"That's a pity...... Grantis sighed, "John, you're the most mathematically gifted kid I've ever met, and I don't want to see you spend your time on those meaningless magic mods...... But, I know, my request is not fair to you......"

"Thank you for your understanding......" Donner was slightly embarrassed.

"Alas...... I can understand it, I just think it's a pity...... You are only a third-level magician, and even if the Superintendent Society can provide potions, it will only allow you to be promoted to a seventh-level magician at most...... But then you won't have time to build a magic model, and that's really unfair to you......" Grantis still frustrated though he understood Donner's choice.

"My lord," Donner looked at Grantis in surprise, "You just said that the Governor Society can provide a potion to promote me to a seventh-level magician?"

Hearing Donner's question, Grantis felt a glimmer of hope and immediately explained: "Yes, the members of the Superintendent Society have dedicated their time to knowledge and truth, so for the low-level mages who join the Superintendent, we provide all the potions before being promoted to the seventh level of magicians for free, which is a special case in the entire Magic Continent. ”

"No need for a magic test?" Donner asked incredulously.

"Yes," Grantis said in a somewhat gloomy tone, "the young people of the Overseer Society don't have time to build magic, and if there is an exam, no one will be able to pass the ......"

The reason why Grantis spoke in a low tone was because once he gave up building magic, it was equivalent to giving up the path to promotion after the seventh-level mage, which was unacceptable for any gifted child. So, even with this provision, he never convinced a genius with it.

However, Donner's next words surprised Grantis a little.

"My lord, I would like to join the Overseer," Donner said firmly, "if you can convince Master Kraft." ”

"What's the difficulty, after you join the Inspectorate Society, you can still retain the student status of the Fire Sacred Academy and represent them in the Five Colleges Examination. At this point, Grantis did not forget to add, "John, you have to think about it." After joining the Inspectorate, I had to work in the Association every day, and I really didn't have that much time to build a magic model. ”

"I've got it figured!" replied Donner, cheerfully.

(Ask for a commuter pass!Recommend a ticket!) (To be continued.) )