How to write x = [x1, x2. Xn] in MATLAB?

How to write x = [x1, x2. Xn] in MATLAB?

X=[x1,x2.Xn]
That's what you wrote above, which means to make these arrays into an array!

Matlab solves the equation with unknown coefficients, just like y = X1 * x ^ 3 + x2 * x + X3 * x ^ 2 + x4, where x1, X2, X3, X4 are unknown coefficients, that is, by solving the equation y = 0, the final form of the solution is x = a * X1 + b * x2 and so on. I hope you can help me,
The final form of the solution is x = a * X1 + b * x2 + C * X3 + D * X4 and so on

syms x1 x2 x3 x4
solve('x1*x^3+x2*x+x3*x^2+x4=0','x')

4(2x^2 − x +1)(x^2 + 3 − 2x) − (3x^2 − 3x + 4)^2

We can see that the last formula with X is the sum of the first two formulas with X. for convenience, the first formula 2x ^ 2 &; X + 1 is expressed as a, the second formula x ^ 2 + 3 &; 2x is expressed as B, then the third formula is a + B, then the original formula is 4AB - (a + b) ^ 2 = (a-b) ^ 2, and a, B is brought into - (x ^ 2 + X-2)

The population of India has surpassed that of China,

At present, the total population of India has reached 1.21 billion, which has increased by 181 million in the past 10 years
The United Nations estimates that India's population will exceed China's 1.34 billion by 2030

A problem of Coulomb's law
Two point charges QA and QB with mass of M and 2m are respectively placed at a and B points on the horizontal plane of smooth insulation. The two point charges are released at the same time. The acceleration of QA is a when they are just released. After a period of time (the two charges do not meet), the acceleration of QB is also a, and the velocity of QB is v. calculate the velocity and acceleration of QA at this time
It's better to write about how to analyze it. Another question is to find the kinetic energy added by the system composed of QA and QB during this period

It is assumed that the Coulomb force between two charges is f at the time of release and f after a period of time
Then we can get a = f / M = f / (2m), that is, if f = 2F, we can get two kinds of charge
After a period of time, the acceleration of QA should be f / M = 2A
By grasping the smooth insulation, we can get the conservation of momentum. Because the velocity of two charges is 0 at the beginning, the sum of momentum of two charges is 0 after a period of time. Thus we can get the velocity of QA is 2V
Since the initial velocity is 0, the kinetic energy of the system is the sum of the kinetic energy of the two charges over a period of time

November 1, 2006 is Wednesday. Can you work out the day of the first day of next month? How many days of class and rest have you had during this period?

There are seven days in a week. November 1 is Wednesday, and November 8 is also Wednesday. Similarly, November 15, November 22 and November 29 are all Wednesdays
In this way, there is a weekend from November 1 to 8, with two days off. Similarly, there is a weekend from November 8 to 15, 15 to 22, and 22 to 29, with two days off
November has 30 days in total, and the 30th is Thursday. During this period, there are four weekends and eight days off, and the rest 22 days are in class
November 30 is Thursday, so December 1 is Friday

Regular expressions in JS can only be Chinese characters, numbers, letters, underscores (can't contain other symbols and full angle symbols)?

/^[\u4E00-\u9FA5\w\d]+$/u
\U4e00 - u9fa5 means Chinese
\W stands for letters and underscores
\D is a number
Note: for this regularization to work, your web page must be UTF-8 encoding, otherwise the Chinese part is invalid

1 divided by (2 Square-1) + 1 divided by (4 Square-1) +... 1 divided by (100 Square-1)

1 divided by (2 Square-1) + 1 divided by (4 Square-1) +... 1 divided by (100 Square-1) = 1 / 1 × 3 + 1 / 3 × 5 +... + 1 / 99 × 101 = (1 / 2) × (1-1 / 3 + 1 / 3-1 / 5 +... + 1 / 99-1 / 101 = (1 / 2) × 100 / 101 = 50 / 101

A topic of permutation and combination in senior high school mathematics
A restaurant provides meals for guests. Each customer can choose two meat and two vegetables from the dishes provided by the restaurant. Now the restaurant has prepared five different meat dishes. If more than 200 different choices are guaranteed, how many different materials should the restaurant prepare?

If C52 * cn2 is greater than or equal to 200, the solution is 7

How to calculate 66 * 66 + 33 * 68

Original formula = 66x66 + 33x (66 + 2)
=66X66+33X66+66
=66X（66+33+1）
=6600