The meaning of tune_ Word formation_ How to read it_ What is phonetic alphabet_ Explanation in dictionaries - Chinese Dictionary

The meaning of tune_ Word formation_ How to read it_ What is phonetic alphabet_ Explanation in dictionaries - Chinese Dictionary

Cavity - full cavity, oral cavity, tone
What's going on
The hollow part of an animal's body: the son
2. Hollow part of utensils
3. Tune of music: tune
4. Voice and intonation

A word has two pronunciations
Luck has two pronunciations, one is soft and the other is the fourth

The light tone is a noun, which refers to one's fortune; the fourth tone is a verb, which is often used by people who study Qigong

Explain words and sounds
Guidelines:
Highlights:
From all aspects:

Guide: 1. The best way to solve a problem or do a good job. For example: Travel Guide, life guide. 2. Metaphor guide, direction. Selected works: Zhang Heng. Tokyo Fu: despicable to give, not to learn, but to get lost. I'm glad to see the guide to my son
Shi two tones, Cui four tones:
Mianmian (mianmianmian four tones, Guan one tone): it means to observe things in many ways

If the square value of X of fraction x-3 is 0, find the value of X

3

It takes five hours for a car to transport goods from place a to place B. It takes three times as long to go as it takes to come back. It's 17 kilometers slower to go than to come back. How many kilometers does the car travel?
From a to B, it takes 2 hours for a and 1 hour and 40 minutes for B. If a starts from a for 8 minutes and B starts from a to catch up with a, how many minutes after B starts to catch up with a?

1. Let's go at the speed of X km / h, and it takes 5 hours to go back and forth, and it takes 3 / 2 times as long as it takes to go back, so it takes 3 hours to go back, and it takes 2 hours to go back. 3x = 2 (x + 7), and it gets x = 14, so the car goes back and forth for a total of 84 km. 2

Is it necessary to list several equations when there are several unknowns?
For example, x ^ 2 + y ^ 2 = 0 only need to list 1 equation?

1、 The quadratic equation is basically like this
I'm afraid we can't solve the cubic equation
If the number of equations is less than the number of unknowns and you want to get a unique solution, you need special problems, such as three unknowns and two equations. You can just eliminate one unknowns or just solve one unknowns. For example, x ^ 2 + y ^ 2 = 0, you only need to list one equation because there are potential conditions

How does a spaceship change speed and direction in a vacuum?

It's combustion boosting. It's liquid hydrogen and liquid oxygen
The principle is that in vacuum, the steam ejected later is ejected to the steam ejected first, and the force is mutual, so the spacecraft obtains the reaction force. Even if there is only a little force in vacuum, it will have action
If any independent system applies force in one direction, it will receive force in the opposite direction;
This effect is defined as the principle of force and reaction, which is a basic principle of practice and cannot be proved - at least so far;
Therefore, as long as the matter is released in one direction, it will be affected by the force in the opposite direction and turn; its specific time effect is called the principle of conservation of momentum and space effect is called the principle of conservation of energy; these are also the basic conservation principles, which are proved correct by practice;
Turning in vacuum is to use the principle of momentum conservation, the rocket ejects high-speed material flow in a certain direction to produce momentum in this direction, so as to produce the same amount of momentum in the opposite direction
This problem aims at the basic principle of physics, that is, only experiments prove that it is true, but there is no reason; if you can find the practice that violates this principle, the whole modern physics will be overthrown - that is, as long as the real air releases matter in a certain direction, it will turn back to its opposite direction, which is a basic physical practice, So far, human beings don't think there is any internal reason for this phenomenon, so we should abstract this universal physical phenomenon as the principle of force and reaction and the principle of conservation of momentum. Don't go against it, otherwise you will get to the top

Make an equation according to the following conditions. Thank you very much. Let's set the unknowns
(1) Five times x is 12 times more than two times
(2) Two thirds of a number is five less than its reciprocal

（1）
5x-2x=12
3x=12
x=4
(2) Let a number be X
2X of 3 + 5 = 1 of X

The size factor of sliding friction
Besides the pressure and the nature of the contact surface, what other factors are related to the sliding friction force?

1. Definition of sliding friction: when an object slides on the surface of another object, it will be hindered by another object. This force is called sliding friction
2. The conditions of sliding friction force are as follows
① Rough contact surface
② Two objects touch each other and squeeze each other
③ There is relative motion between objects
3. The magnitude and direction of sliding friction:
① Direction: always tangent to the contact surface, and opposite to the direction of relative motion of the object. The so-called relative motion is still based on the reference frame of the object exerting the friction force
② Size: the size of sliding friction f is proportional to the positive pressure, that is, f = μ n. μ is the dynamic friction coefficient: it is related to the material and roughness of the contact surface, and the roughness of the contact surface and the elastic force between the contact surfaces
③ The magnitude of sliding friction is slightly smaller than the maximum static friction Fmax. In general calculation, it can be considered that the maximum static friction is equal to sliding friction
Note: the sliding friction is independent of the contact area

It is known that equation 3x-2 and equation 12 / A-1 = 8 / X have the same solution for X, so we can find the value of A

It seems that the title is incomplete. Equation 3x-2? This is just an algebraic expression. Did you miss it?
Or the equation 3x-2 = 12?