Lan Xiaoya's eyes widened and asked a little confused.

"May I ask Lord Wang, what is calculus? I've never heard of it. ”

Lu Ning smiled and replied.

"It's the problem of studying the maximum and minimum values in equations, and algebraic knowledge is required here, I wonder how much Miss Lan has learned?"

In fact, most of the ancient mathematics was practical, and there was little theoretical knowledge, and the geometry of Western Euclid was originally translated in the last years of the Ming Dynasty.

As for "Fang Yuan's Illustration of the Dark", which expounded the knowledge of calculus, it was not written until after the birth of Li Shanlan, a mathematician in the late Qing Dynasty.

Even Li Shanlan's achievements in calculus are far inferior to Newton and Leibniz.

Because the higher the level of mathematics, the less calculations involving specific values, most of them use algebraic knowledge.

Lu Ning thought for a while, picked up the pen, and wrote the three letters of XYZ on the paper that expressed the unknown. Then the Arabic numerals from zero to nine were written.

Lan Xiaoya looked at it: "What are these?" ”

Lu Ning told him that these are Arabic numerals below, because they are quite concise compared to Chinese characters with many strokes, so they are used in mathematics.

The other party thought about it and felt that writing Chinese characters with a pen was not necessarily slower than him, although he felt that this idea was strange, but he didn't think it was a big deal.

Lu Ning said again that the three letters on it represented unknown numbers, and then wrote him calculation symbols such as addition, subtraction, multiplication, division, and equal signs, and told her how to list the equation.

Lan Xiaoya smiled and replied.

"In the Tianyuan technique, the use of the three elements of heaven, earth, and man to represent the unknown is similar to this strange code of yours, and there is nothing unusual."

Lu Ning thought about it and said again.

"Do you know what exponential is and logarithm is? Do you know what a sine cosine is? Do you know what rational numbers are, irrational numbers, real numbers, and imaginary numbers? What is a primary function and what is a transcendent function? ”

At this moment, Lan Xiaoya was stopped, and she said with wide eyes.

"These little women have never learned, and they ask the prince to teach them."

Lu Ning actually fooled her, so he smiled again.

"In fact, to solve the system of equations, you don't have to calculate it originally, you can use the image method to solve it directly, if you don't believe it, please Miss Lan come up with a problem, and I will demonstrate it to you."

Lan Xiaoya's eyes rolled, and she remembered a famous question in ancient times.

"There are thirty-three tripods and tables today, a total of one hundred, how many tripods are there, how many tables are there?"

The Ding has three legs, and the table has four legs, and knowing the total number and the number of legs, you can solve the problem by simultaneous equations.

But Lu Ning wanted to show the mystery of functions, so he used the function method.

Lu Ning picked up the pen, changed to a plane Cartesian coordinate system, marked the axis, and then wrote two functional formulas.

drew an image of the function in the coordinate system, and then pointed to the intersection of these two functions, and said to Lan Xiaoya.

"Miss Lan, please see, the intersection of these two straight lines is the solution to this problem, there are thirty-two tripods and one table."

Lan Xiaoya secretly exclaimed in her heart, she could solve this kind of problem if she changed it, and the speed was not slower than Lu Ning.

It's just that the so-called functional image method is indeed unheard of and unheard of.

She thought about it, and then changed the coordinate axis in her own way, and then wrote a horizontal axis marked as the earth axis, and marked the digging well as the sky axis.

I also drew the scale on the coordinate axis, and drew two straight lines like Lu Ning.

"Lord Wang, you are really a god and a man, this kind of image method, no one of the ancients could have imagined, in time, you will inevitably become a generation of grandmasters, please come to my room to talk about it."

As he spoke, he was going to invite Lu Ning to his boudoir.

At this time, the apricot next to her was anxious, and said that there is a difference between men and women, how can a girl's boudoir be a strange man's casual entry?

Once the old lady knew about this, she had to be furious, so she was so frightened that she quickly knelt in front of Lan Xiaoya and said.

"Miss, this is not in line with etiquette, please think twice."

Lan Xiaoya was originally a girl who obeyed the rules, but just now she just admired Lu Ning's talent, so she wanted to invite him over to teach her.

I was so anxious for a moment that I forgot the restrictions of etiquette and couldn't help but blush.

Lu Ning also felt that it was unseemly to enter the girl's boudoir recklessly, and seeing Xing'er blocking the road was exactly what he wanted.

"In the lecture hall, I have prepared an elegant apartment for Miss Lan, as well as a separate office, if Miss is interested, please go and teach. If I ask an academic question in the office, I will know everything and say everything. ”

Seeing that Lu Ning didn't mean to laugh at herself, Lan Xiaoya relieved herself.

After calming his heartbeat and carefully organizing his words, he replied.

"Thanks to the prince's weight, the little woman will definitely obey her fate, please wait a while, I will pass."

At this time, Lan Yu, who had gone out on business, walked back. I heard that the king of Changning was also coming, so he was going to come out to meet him.

At this moment, a maid suddenly came to report.

"Grandpa Qi, Madame, please."

Lan Yu didn't know what was going on, so she said to Lu Ning that she was not with her, ordered her son to entertain Lu Ning in the living room, and hurried away in the backyard.

When I walked to the back hall, I saw that the three ladies were there, and when I saw him come in, I hurriedly saluted him.

Madame Shepherd is the main wife, and the other two are equal wives.

"Master, our daughter has a sweetheart, you should be happy."

Lan Yu was stunned in her heart and said hurriedly.

"Xian'er, you say? Didn't he already promise His Royal Highness the King of Shu as a concubine, what else does he need to say? ”

It turned out that Lan Xiaoxian, the eldest daughter born to Mrs. Mu, had already been married to Zhu Yuanzhang's son, Zhu Chun, the king of Shu, which was no secret.

Madame Mu smiled slightly and said.

"It's not Xian'er, but Xiaoya, born to Mrs. Hu, already has someone she likes, and she just asks the master to call the shots."