On the system of linear inequalities of one variable 1、 In the system of equations {2x + y = 1-m, if the unknowns X and y satisfy X-Y < 0, then the value range of M is———— x+2y+2 2、 If the solution set of inequality system {x-a ＞ 2 is - 1 ＜ x ＜ 3, then a = -, B=___ x-b＜1 3、 Box 700 pieces of products. If 15 pieces are packed in each box, more than 3 boxes of products can not be packed. If 20 pieces are packed in each box, at least 8 boxes are left. Calculate the number of boxes. (the solution of the formula) 4、 Given that the solution X and y of the system {2x + y = 5m + 6 are all positive numbers, the value range of M is obtained. x-2y=17

On the system of linear inequalities of one variable 1、 In the system of equations {2x + y = 1-m, if the unknowns X and y satisfy X-Y < 0, then the value range of M is———— x+2y+2 2、 If the solution set of inequality system {x-a ＞ 2 is - 1 ＜ x ＜ 3, then a = -, B=___ x-b＜1 3、 Box 700 pieces of products. If 15 pieces are packed in each box, more than 3 boxes of products can not be packed. If 20 pieces are packed in each box, at least 8 boxes are left. Calculate the number of boxes. (the solution of the formula) 4、 Given that the solution X and y of the system {2x + y = 5m + 6 are all positive numbers, the value range of M is obtained. x-2y=17

1： M > - 1 2: a = - 3, B = 2 3: if the number of boxes is x, then 700-15x > 3x15700-20 (X-8) ≤ 0, then x0, Y > 0 can be obtained. Let equation [1] be. 2x + y = 5m + 6, equation [2] be. X-2y = 17, equation [1] - 2 [2] be y = M-28 / 5 > 0, equation [1] + [2] be x = 2m + 29 / 5 > 0, equation [2] be. Finally, equation [2] is

On the application of linear inequalities of one variable
If there are 4 chickens in each cage, there is one chicken outside the cage; if there are 5 chickens in each cage, there is one cage without chicken. How many chickens are there in each cage?
Note: it is not a linear equation with one variable, but an inequality with one variable
Please write down the process of thinking and solution, and write down the process of your understanding,
Wrong answer on the third floor
The inequality of degree one variable

With X cages, the total number of chickens is 4x + 1
According to the second condition, there are 5 chickens in the first (X-2) cage, while there are ≤ 5 chickens and ≥ 1 chickens in the other cage
The inequality is obtained
5≥（4x+1）-5（x-2）≥1
The solution is 10 ≥ x ≥ 6
X is an integer 6 7 8 9 10
The number of chickens was 25 29 33 37 41

The two tangents passing through the moving point P on the ellipse x ^ 2 + y ^ 2 = 1 (a > b > 0) to the circle O: x ^ 2 + y ^ 2 = B ^ 2 are PA and Pb, and the tangents are a and B respectively
The two tangent lines from the moving point P on the ellipse x ^ 2 + y ^ 2 = 1 (a > b > 0) to the circle O: x ^ 2 + y ^ 2 = B ^ 2 are PA and Pb, and the tangent points are a and B respectively. The line AB intersects the X axis and Y axis at M and N respectively. The minimum area of the triangle mon is obtained

Here we need to know: if the equation of the circle is X & sup2; + Y & sup2; = R ^ 2, and the point m (x0, Y0) is outside the circle, we prove that the linear equation of the tangent chord of the point m about the circle is x0 * x + Y0 * y = R & sup2; we prove that if two tangent points are a (x1, Y1), B (X2, Y2), then the tangent passing through point a is X1X + y1y = R & sup2; the tangent passing through point B is X1X + y1y = R & sup2

If the univariate quadratic equation (M + 5) x ^ 2-2 (M + 2) x + M = 0 about X has no real root, the case of the univariate quadratic equation MX ^ 2-2 (m-2) x + (m-5) = 0 root about X is judged

The first one has no real roots
[-2(m+2)]^2-4*(m+5)*m4
The second equation
{-2(m-2)]^2-4*m*(m-5)=4(m+4)>0
So there are two unequal real roots

The land area of the United States is larger than that of China, ranking third in the world, next to Russia and Canada?
Always thought that China is bigger than the United States, today read Baidu Encyclopedia, it said that the United States is bigger than China
That's territory, not territory

Today, the U.S. Central Intelligence Agency announced on its website: "China's land area is 9.59696 million square kilometers, while the U.S. land area is 9.631418 million square kilometers. We are 34.458 million square kilometers less than the United States. Therefore, China's area is not the third only after Russia and Canada, but the fourth after the United States."
In response, Professor Cui Haiting of the school of environment, Peking University and Chen Jun, director of the National Center for basic geographic information, said: "China's land area is 9.6 million square kilometers. In the Encyclopedia Britannica, China's land area is 9.5729 million square kilometers, and the area of the United States is 9.518287 million square kilometers, which is smaller than that of China." at the same time, the State Bureau of Surveying and mapping told reporters: "accurate statistics have been completed, It will be announced in due course. "
After reading these news, I don't know how readers feel. I have some ideas about it
As early as the 1940s, when I was in primary school, my geography teacher told me that China's territory is like a mulberry leaf, covering an area of more than 10 million square kilometers. I can't remember how much more. Later, I didn't know when Outer Mongolia was independent. After my little grandson studied, my teacher told me that China's territory is 9.6 million square kilometers
9.6 million is an integer. Is it really an integer of no more or no less?
Unfortunately, when the intelligence agency said that China's land area is not the third but the fourth, our professors still hold on to 9.6 million, and even quoted the Encyclopedia Britannica of that year to prove that we are the third and the United States is the fourth
What's more, the State Bureau of Surveying and Mapping said: "accurate statistics have been completed and will be released at an appropriate time."
It should be said that today's surveying and mapping technology has advanced by leaps and bounds. We can accurately map the world's highest peak, but can't we clearly map our territory? Now, people have mapped our territory clearly. It's the 57th anniversary of the founding of the people's Republic of China, but we still can't tell the people our country's territory. What's the matter? Of course, China has gone through many wars, Our territory is being carved up by others, while the territory of the United States is expanding. It is probably the result of reclamation!

Why does Coulomb's law hold in vacuum

Because if there is air (or other medium), it will affect the coefficient of Coulomb's law

On May 12, 2008, an earthquake with a magnitude of 8.0 occurred in Sichuan, China?

There are 365 days in a year, 7 days in a week, and the cycle is 52 times backward, that is, after 52 * 7 = 364 days, there are 365 days in a year. After adding one day, Monday becomes Tuesday
This is the second time I have answered

In order to find the chemical equation of carbon dioxide production in junior high school, we need to balance it, and we also need a literal expression

CaCO3+2HCl=CaCl2+H2O+CO2↑
Calcium carbonate + hydrochloric acid = = = calcium chloride + water + carbon dioxide

Factorization 10000 / 252 ^ 2 * 48 ^ 2

10000/252^2*48^2
=（10/252）^2*48^2
=(5/126)^2*48^2
=(5/126*48)^2
=(40/21)^2
=1600/441

A mathematical problem of permutation and combination plus probability
There are nine balls in a bag, including three white balls and six black balls. Take n balls out of the bag and ask, what is the probability that n balls contain all three white balls when the probability is closest to 50%?

If there are 3 white balls in n balls, then there are no white balls in the remaining 9-N balls. There are 9! / ((9-N)! N!) ways to take n balls out of 9 balls. Among them, 3 white balls come from n balls, and 6! / ((9-N)! (- 3 + n)!) ways to take the other n balls from 6 black balls