In the evening, Yu Wenwen, who had just finished the military discussion, entered the city again, ate a few cooking cakes and drank a few bowls of porridge at the accommodation in Wuyang City, and continued to pick up guests... The guests he wants to meet this time are civilians, and the things he wants to discuss are both public and private.

Wang Yue and several Huangzhou businessmen waited for most of the day in the Wuyang official office, and finally met the king of Xiyang (the big owner) at this time, so they had a thick stack of materials in their hands and prepared to report to Yuwenwen.

Yu Wenwen is very busy, so he doesn't have time to talk nonsense, his opening remark is "The principal is about to be in place, and the next step can begin".

The so-called "principal" means that when Yuwen Wen met with the sons of Haoqiang in various places in the afternoon, he proposed to "borrow" from various clans, and these clans must lend materials of varying amounts to the officials and soldiers within five days, which is the "principal".

Yu Wenwen got this material, which is expected to be discounted by more than 1.5 million yuan, which can be used to supplement military supplies, but there are two ways to use it.

The first way is to directly use these materials as military supplies, which is simple and straightforward; The second method is "capital operation", after a series of operations, two cents can be spent at least three cents.

The second option sounds good, but it is risky to implement, that is, once encountering "force majeure", it may mess up, and it is not as safe as the first option.

After comprehensive consideration, Yu Wenwen chose the second method, that is, to deposit the borrowed materials into the Rixingchang cabinet, so that the Rixingchang cabinet and others could also make a fortune on the premise of ensuring military supplies.

On behalf of the Huangzhou Governor's Office, he borrowed money from Haoqiang in various places at an interest rate of 10%, and deposited it in the Rixingchang Cabinet Workshop at a deposit interest rate of 5%, and the Rixingchang Cabinet Workshop lent money at an interest rate of 20% to the workshop owners in various places, so that they could expand production and recruit more people.

It is also necessary to lend money to the owners of Xinwu Fort in various parts of Huaixi, so that they can have sufficient material support for the smooth completion of the autumn harvest, and the grain harvested in these places will be the key to ensuring the march and operation of the Lingnan Road.

Yuwenwen carried out capital operation in this way, which is to make the role of this material play to the extreme.

He put down the information and asked, "Can the loan interest of 20% ensure that Rixingchang does not lose money?" Can you make sure that the borrower will not lose money after repaying the money? ”

Wang Yue replied when he heard this: "Your Majesty, please rest assured, this interest has been calculated, and there will definitely be no loss, and there will even be a slight surplus." ”

"The formula is complicated and updated, so you can't be sloppy."

"The king can rest assured, the new formula has been skillfully used by the shopkeepers, and the results calculated from this are absolutely no problem."

Yu Wenwen picked up the information again: "There are no absolutes in the world. ”

"What the king said is that the grass people are abrupt."

As soon as Wang Yue's words fell, Yu Wenwen looked at the person beside him and asked, "Tell me about Huaixi's lending situation." ”

"Yes, King..."

Follow Wang Yue to meet several businessmen of Xiyang Wang, and began to introduce the details of the capital operation to Yuwenwen, and the "formula" they said is a magical financial management formula: the interpolation formula.

To be precise, the formula is unequally spaced cubic interpolation.

This formula was proposed by Liu Zhuo, one of the two Lius, and was originally used for the compilation of the astronomical calendar.

The interpolation method, also known as the trick technique, is the "surplus and deficiency technique" in the Han Dynasty mathematical work "Nine Chapters of Arithmetic", which is equivalent to the one-time difference interpolation method (linear interpolation).

Since the Han Dynasty, astronomers of all dynasties have tried to compile the most accurate calendar, and they regard the apparent movement of the sun and the moon as uniform, and it is of course relatively simple to calculate the movement of the sun and make up the calendar on this premise, but it is not accurate.

Zhang Zixin, an astronomer at the end of the Yuan and Wei dynasties, found that the sun moves slowly after the vernal equinox and fast after the autumnal equinox through long-term observation of celestial phenomena. This fact has prompted astronomers to devise new methods for calculating the sun's motion, among other things.

Liu Zhuo, who is famous for his literature but is also proficient in mathematics and astronomy, on the basis of Zhang Zixin's theory and inspired by the primary interpolation method in the "Zhou Ji Sutra", first used the equally spaced quadratic interpolation formula in the astronomical calendar to improve the calculation accuracy.

Liu Zhuo used the equal-spaced quadratic interpolation method when calculating the sun, month, and five-star rows, and divided the year into 24 equal time intervals as the independent variable, and each interval was regarded as the length of time between the two solar terms.

Liu Zhuo believes that the motion of the sun is uniformly accelerated, so the calculation of the apparent degree of the sun should be calculated by using the equally spaced quadratic interpolation method.

Yu Wenwen, who has basically forgotten all about mathematics, can't understand the meaning of this formula deduced by Liu Zhuo at all, but he questioned Liu Zhuo's definition of "the time interval of the twenty-four solar terms in a year is equal".

After numerous academic debates, Liu Zhuo realized that his views might be wrong, so he improved the calculation formula of the interpolation method again.

The equally spaced quadratic interpolation formula evolved into the "unequally spaced quadratic interpolation formula".

As a result, Liu Zhuo revised the new calendar he had painstakingly compiled, and Yu Wenwen was not interested in this "unequal spacing quadratic interpolation formula", because even if he understood it, he did not plan to participate in the compilation of the calendar.

However, after pondering this formula, Wang Yue, the big treasurer, found that the interpolation method has other uses, that is, financial management and wealth management (capital operation) to maximize the benefits of an investment.

To use a more 'professional' term, it is to use interpolation to calculate the yield.

Example 1, calculating the discount rate, a wealthy man Zhang San, wants to save money in Rixingchang Cabinet to eat interest, his idea is to deposit 5,000 yuan, and after five years, he will have to have 7,500 yuan with principal and interest, so how much does the deposit interest have to reach in order to achieve his financial goals?

Example 2: Li Si, a resident of Xiyang City, has an idle small yard on hand, and he has two choices, one is to rent the yard, and the other is to sell the yard directly.

If the yard is rented, the rent needs to be charged at the beginning of each year, assuming that the income from the sale of the house is deposited in the cabinet shop, the interest is 10%, and the repair cost of the house in the yard is not counted.

In this case, how many years does Li Si have to rent the yard so that the rental income is comparable to the income from the one-time sale of the house (including the interest on saving money)?

Example 3: Calculate the payback period: Wang Wu, a businessman, wants to use his own funds of 10,000 yuan to invest in the construction of a paper workshop, with a construction period of three months and eight years of operation.

The net cash flow generated by the paper mill in the first four years after it was put into operation was 4,000, 3,000, 2,000 and 4,000.

The net cash flow generated in each of the last four years is 3,000 yuan, so how to calculate the payback period including the construction period, and the payback period excluding the construction period?

These three problems can evolve into more problems, which can be solved by accumulators, but in the end, they rely on empirical calculations, and once they encounter a "investment project" with a complex situation and many variables, even profiteers may not be able to figure it out.

With the interpolation method, you only need to substitute the interpolation formula, and the result can be calculated immediately, which is simple and clear.

For the Rixingchang Cabinet that absorbs depositors' funds to lend and make profits, the interpolation formula is a sharp tool for investment and financial management and capital operation.

The equidistant quadratic interpolation formula proposed by Liu Zhuo and the unequal quadratic interpolation formula improved on this basis have been found to be indeed "miraculous" after the actual operation and inspection of the shopkeepers.

The "unequal cubic interpolation formula" deduced by Liu Zhuo and other scholars made Ri Xingchang more powerful when carrying out lending and investment business, and the interpolation formula originally used to calculate the astronomical calendar became a magic weapon for Yuwenwen to make profits.

This is the power of mathematics, Yuwenwen wants to operate capital this time and eat more fish, and the confidence comes from the interpolation formula that has been tested in practice.

The problem is not nothing, the premise of everything is that he cannot defeat the battle, in the final analysis, without military victory, where will the benefits be?