People's education press first day mathematics volume II exercise 8.4 on page 114

Reference method: (superscripts ①, ②, ③ of the equation group, substituting ① into ②, we get 11x + 2Z = 23, ④ × 2 + ③, we get 25X = 50, x = 2, we get z = 0.5, we get x = 2, we get y = - 5 (bracket expansion x = 2, y = - 5, z = 0.5) comment on 57 questions of mathematics book exercise 8.2 of the seventh grade volume of pep

Grade one mathematics volume II people's education press 119
Practical questions,

Exercise 4.2 knowledge and skills 1. P (Xiao Ming goes to the cinema) = 1 / 2p (Xiao Li goes to the cinema) = 1 / 2. Because 1 / 2 = 1 / 2, the game is fair to both sides. Mathematical understanding 1. PS: the answer to this question is not unique. The following answer is only for reference. You can also use the coin tossing method 2. PS: the answer to this question is not unique. The following answer

Mathematics navigation in grade one of junior high school, question 8, page 81 (people's Education Press)
A graphic problem,

AOB, AOC = 80 degrees + 2aom + AOB, because OM is the bisector of AOB, so AOB = 2aon, because OM is the bisector of AOB, so AOC = 2aon, because AON + AOC = 180 degrees, so 2aom + 2aon = 180 degrees, because mon = 40 degrees, Aon = mon + AOM, so 2aom + 2aon = 180 degrees, 2aom + 2aom + 2 times 40 degrees = 180 degrees, 4aom + 80 degrees

If the function y = x squared (x ≤ 3), y = 2x (x > 3), y = 9, then the value of the independent variable x is?

If x ≤ 3, y = x & # 178; = 9, then x = - 3 or x = 3 is acceptable;
x> 3, y = 2x = 9, x = 4.5 is also acceptable
To sum up, the value of X is: x = - 3 or x = 3 or x = 4.5

How to calculate 23 * 15 69 * 45

23*15=(20*15)+(3*15)=345
69*15=(70*15)-(1*15)=1035

1,0,-3,0,5,0,-7,0…… What is the general term formula?

The general formula is as follows:
=((n-INT(n/2)*2)*(-1)^INT(n/2))*n
In Excel, select column a, select menu insert - name - definition, enter n in the definition name dialog box, and click OK;
Enter 1, 2, 3,... In column a
Copy the formula = ((n-int (n / 2) * 2) * (- 1) ^ int (n / 2)) * n to column B, and compare it with column a 1, 2, 3 In the corresponding cell, the calculation result can be obtained

Partial derivatives ZX, ZY of implicit function determined by equation x2 + Y2 + z2-4z = O

First, we take the derivative of X,
2x+2zz'-4z'=0
x=2z'-zz'
z'=x/(2-z)
For y, 2Y + 2zz '- 4Z' = 0
y=2z'-zz'
z'=y/(2-z)

How to detect the content of acetic acid in liquid

In fact, infrared NMR can be tested to see how accurate you need
The boiling point of glacial acetic acid is 118 ℃
But this is direct injection, you have to see what substances are in your liquid, how the boiling point, if the boiling point is too high, you can not direct injection, to use headspace

Physics problems in grade two of junior high school
Who can help to talk about the pulley part? It's urgent. There's a lot of reward. Just make it clear_

In short:
The fixed pulley changes the direction of force without saving effort, which is essentially an equal arm lever
The movable pulley saves half of the force, which is actually a lever with power arm twice as much as resistance arm
Winding mode:
Odd even fixed (when the number of rope segments is odd, the pulley shall be wound first, and when the number is even, the pulley shall be wound first)
The pulley block saves labor but not work,
Mechanical efficiency of pulley block: g / NF, G: weight gravity, N: number of rope segments, F: free end tension

What is the LN (LNX) formula equal to

Y = ln (LNX) is a function, the domain of definition is (1, + infinity)

People's education press first day mathematics volume II exercise 8.4 on page 114