After wandering in the valley for a long time, everyone finally rode their horses and slowly walked towards Chang'an City.

After entering the palace, Li Tai hurriedly asked Li Fugui to get himself a pot of Buddha jumping over the wall to suppress the shock and replenish calcium.

After dinner, Li Tai was called by Li Shimin to the inside of the imperial study.

Li Tai was very puzzled, what is the matter?

"I said, dear daddy, what's wrong with you?" Li Tai asked, "If it's okay, I'm going home." ”

"Hmph, do you hate staying with me so much?" Li Shimin snorted coldly and said.

"Well...... Can I say yes? ”

"Huh?"

"Dad, we've been together for so long, you're not tired, I'm tired of it, I've grown up, give me a little space, a little freedom, okay?" Li Tai looked at Li Shimin and sang helplessly: "Forgive me for my unruly indulgence and love for freedom in this life......"

"The devil cries wolf." Li Shimin glared at Li Tai, then took out a piece of paper, spread it on the table, and said, "What do these symbols mean?" ”

"That's 123456789."

"One, two, three, four, five, six, seven, eight, nine?"

"It's Arabic numerals."

"Arab?"

"Forget it, it's a simple symbolic number." Li Tai said: "The number used for calculation, this number is much more convenient than our Chinese character calculation." ”

"Oh? Let's hear it. Li Shimin was immediately interested.

Li Tai was very puzzled, where did he get these things?

Oh yes!

When I was designing the hot air balloon, I had these numbers in the design drawing, and it seems that my father took them.

"Let me give you an example, for example, if you add two by two, one thousand three hundred and eighty-two plus three thousand four hundred and fifty-one equals eight thousand four hundred and thirty-three." Li Tai began to list them with Li Shimin: "And it is much simpler to write this: 1382 + 3451 = 8433......"

Li Tai gushed and listed, and Li Shimin nodded again and again when he listened.

At this time, it was already the middle of the night, and Li Shimin was still a little unsatisfied.

Finally, Li Tai couldn't help it.

"Dad, I'm so sleepy, when I'm still growing my body, why don't I go back to sleep first and explain to you tomorrow?" Li Tai asked tentatively.

"Yes." Li Shimin nodded and said, "It's really late, so let's do it, you will sleep in the palace tonight, and one day you will finish writing this "Zhenguan Arithmetic", and then it will not be too late to return home." ”

"What's even "Zhenguan Arithmetic"?" Li Tai was very puzzled.

"Yes." Li Shimin's fingers tapped on the paper full of arithmetic, and said, "How can such a mysterious arithmetic be available in Fanbang?" This is the art of the prosperity of my Tang Dynasty, which should be called "Zhenguan Arithmetic". ”

"Dad, can we have a face?" Li Tai was really convinced.

Zhenguan paper and Zhenguan lamp are forgotten, and now there is a Zhenguan arithmetic.

Dad, is this shamelessness genetic?

Li Tai was really speechless.

"Hmph, I am the Ninety-Five, I said that "Zhenguan Arithmetic" is "Zhenguan Arithmetic". Li Shimin said proudly.

"Dad, you're floating, floating, it's not good, it's not good." Li Tai couldn't help but shake his head and said, then turned around and ran outside.

If you say you won't let me go home, I won't go back?

Just kidding, I'm not going to sleep in your palace.

I don't have a girl to sleep with, I can't sleep!

"Hmph, this shaft!" Watching Li Tai's figure disappear quickly, Li Shimin couldn't help but snort fiercely, quite a kind of iron.

Li Tai ran back to the house and washed up.

Then, I slept with my fragrant daughter-in-law in my arms.

When I woke up the next day, I started to get busy.

Although I despise my father, I am my backer after all.

It is also beneficial to oneself to be able to increase his prestige.

As the saying goes, hello, hello, everyone.

After eating something, Li Tai began to take ink and white paper and write slowly.

Simple addition, subtraction, multiplication, division.

Ninety-nine multiplication formula.

Unary Linear Equations.

Binary Linear Equations.

Area calculation method.

Volume calculation method.

How to calculate the circle.

……

Although Li Tai was a scumbag when he was in school, he still knew simple mathematics.

And with the help of a computer, it's actually quite easy to put together a booklet.

For several days, Li Tai was busy in the warehouse.

At this time, in the palace.

Li Yuan was looking at an invitation, and his whole person was extremely happy.

"It seems that this Longxi Li family has finally regarded my vein as the real Longxi Li family's descendant, good, good, good." Li Yuan was very happy and said, "This time, I'll take a look, who else dares to underestimate me!" ”

"The Li family in Longxi can come out of our lineage, in fact, it is their glory, think about who of these five surnames and seven hopes can come out of the royal family?"

"But how should this be for the better? To go or not to go? Soon, Li Yuan frowned slightly, and then looked at the eunuch next to him.

"Li Ren, do you think I should go, or shouldn't I go?" He asked.

"Back to Your Majesty, it is better to ask the saint about this matter." Eunuch Li Ren spoke.

"Hmph, why do I need to ask him when I do things?" Li Yuan snorted coldly, obviously very dissatisfied with this eunuch.

……

Chang'an City.

City.

Hu Shang Lu Buwei got up early, took his daughter, and was taking care of the store.

However, there are very few people in the store.

This made Lu Buwei a little worried, whether his advertisement was done in vain, it had been several days, why were there still so few customers?

"Hey, is it really useless?" He couldn't help but sigh, he originally thought it was a business opportunity, but now when he saw this situation, he couldn't help but feel a little puzzled.

However, at this very time.

A brocade-covered figure walked in from outside and asked in a loud voice, "Shopkeeper, did you ever sponsor the opening ceremony of the medical school?" ”

"It's a small shop." Lu Buwei said.

"That's it, your store, it's really hard to find, I thought it was in the East Market, but I didn't expect it to be in the West Market, it's really not easy to find." He said loudly: "Shop, you have some good things in the store, quickly take them out and let me take a look, I don't have much else, but I have a lot of money." ”

"Shopkeeper, quickly bring me a pound of Western Regions fennel beans." At this time, another well-dressed man walked in.

"I heard that your cumin here is quite good, bring me ten catties."

"Do you have black pepper here?"

“……”

Suddenly, there was a lot of excitement with guests.

Lu Buwei is extremely happy, it seems that his 100,000 yuan is not in vain.

The fame of this store has been hit, are you afraid that you will not have money in the future?