![](data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 72 71" width="72"></svg>)
What is a control experiment in the first year of junior high school
1. Blank control
For example, in the experiment of "identification of soluble reducing sugars in biological tissues", test tube solution a is added with reagents, while test tube solution B is not added with reagents. Boiling water bath is used to compare their changes, And B is a typical blank control. The blank control can clearly contrast and contrast the changes and results of real l ~ - Ta, and enhance the persuasion
2. Self control
It means that the experiment and the control are carried out on the same object, that is, there is no other control group. Single group method and round group method generally include self control. For example, the experiment of "separation and restoration of plant cytoplasmic wall" is a typical self control. Self control is a simple method, and the key is to see the difference of phenomenon changes before and after the experimental treatment. The object condition before the experimental treatment is the control group, The experimental group was the experimental group
3. Condition control
It means that although the subjects are given some experimental treatment, the treatment is used as a control, or the treatment is not the meaning of the experimental variable given by the experimental hypothesis, The experimental design was as follows: group A: fed with thyroid hormone (experimental group); group B: fed with thyroid inhibitor (methimazole) (conditional control group); group C: not fed with medicament (blank control group). Obviously, group B was the conditional control, and the experiment set up both condition control and blank control, It can fully explain that the experimental variable thyroid hormone can promote the growth and development of earthworm
4
It means that there is no other control group, but several experimental groups are compared with each other. In the equal group experiment method, most of them are controlled. For example, in the group experiment of "plant tropism", the five experimental groups are compared with each other, which better balances and offsets the influence of irrelevant variables, and makes the experimental results more convincing
How to teach the first English lesson of junior high school?
The first section is to learn letters, a, B and C. The content is very simple, but we should find ways to make students interested. From then on, we will be interested in English
Junior one students are still very small, so some games and activities before class or in class are very effective for them
You can also go to other people's class for reference
wish you success!
The distance between a and B is 560 km, a car from a to B, 80 km per hour; B car from B to a, 60 km per hour? (2) If car a does not leave until 1.5 hours later, how long does it take for car B to meet car a?
(1) Let x hour meet. 80x + 60x = 560, the solution is x = 4. A: if two cars start at the same time, they will meet in 4 hours. (2) let y hour meet. 80 (y + 1.5) + 60y = 560, the solution is y = 227. A: if car a starts after 1.5 hours, car B will meet car a 227 hours after starting
What is the square of M = two and seven ninths?
M ^ 2 = 2 and 7 / 9 = 25 / 9 = (± 5 / 3) ^ 2
M = ± 5 / 3 (plus or minus 5 / 3)
From a to B, Party A and Party B return to B according to the original road, 32 kilometers away from B, and meet Party B. Party A travels 20 kilometers per hour, and Party B travels 12 kilometers per hour. How many kilometers is the distance between AB and Party B
The solution of solving equations
From a to B, Party A and Party B return to B according to the original road, 32 kilometers away from B, and meet Party B. Party A travels 20 kilometers per hour, and Party B travels 12 kilometers per hour. How many kilometers is the distance between AB and Party B
Suppose that the distance between AB and ab is x km
Then (32 + x) / 20 = (x-32) / 12
96+3x=5x-160
256=2x
X = 128 km
So the answer is 128 kilometers
1 * 2 * 3 * 4 + 1 = 25 = 5 ^ 2, 2 * 3 * 4 * 5 + 1 = 121 = 11 ^ 2, 3 * 4 * 5 * 6 + 1 = 361 = 19 ^ 2, then n (n + 1) * (n + 2) * (n + 3) equals?
Decomposition factor n (n + 1) (n + 2) (n + 3) + 1 = [n (n + 3)] [(n + 1) (n + 2)] = (n & # 178; + 3n) (n & # 178; + 3N + 2) + 1 = (n & # 178; + 3n) &# 178; + 2 (n & # 178; + 3n) + 1 = (n & # 178; + 3N + 1) &# 178;
1. The distance between a and B is 720 km. A passenger car and a freight car start from a and B at the same time and run in opposite directions. The passenger car runs 100 km per hour, and the freight car 80 km per hour. A few hours later, the two cars meet? (using equation)
2. The distance between a and B is 720 km. A car and a truck start from a and B at the same time and run in opposite directions. If the speed of the car is 1.25 times that of the truck, after 4 hours, the two cars meet. What are the speeds of the two cars? (also solved by equation)
Can it be a little faster? Oh My God! My homework~·
Let two cars meet in X hours
（100+80）x=720
180x=720
x=720/180
x=4
Four hours later, the two cars met
Let the speed of the freight car be X
（1.25x+x）*4=720
2.25x=180
x=80
80*1.25=100
The speed of a truck is 80 km / h and that of a car is 100 km / h
If the fractional equation 1 has a real solution than x-2-a and X-1, then the value of a cannot be zero
Is it: 1: (X-2) = A: (x-1)?
∴a﹙x－2﹚=x－1
∴ax－2a－x=－1
∴﹙a－1﹚x=2a－1
To have a real solution to the equation,
Then A-1 ≠ 0, that is, a ≠ 1
Two seventh of a is equal to three fourths of B, and the ratio of a to B is ()
Let a be x and B be y 2 / 7X = 3 / 4Y 2 / 7 × X / y = 3 / 4 x / y = 21 / 8
0.125 to the 100th power multiplied by 2 to the 300th power
0.125^100*2^300
=(1/8)^100*(2^3)^100
=(1/8*8)^100
=1^100
=1
RELATED INFORMATIONS
- 1. How to have a good math class
- 2. How to teach the first advanced mathematics lesson in the new term?
- 3. Calculation of the first grade of junior high school 1.180 degrees - (48 degrees 39 minutes 40 seconds + 67 degrees 41 minutes 35 seconds) 109 degrees, 11 minutes, 4 seconds divided by 7 23 degrees 41 minutes 34 seconds times 3
- 4. On angles and the measurement of angles, With your question, "it is known that α and β are obtuse angles. The results of calculating 1 / 6 (α + β) of a, B, C and D are 26 degrees, 50 degrees, 72 degrees and 89 degrees, including the correct results. Then who do you think the correct results may be given? Write clearly
- 5. English Evaluation Handbook for grade one 2、 Translate the following phrases Take time to do sth 3．a member of_________ 4. Chat with each other 5．my favourite lessons_____________ 6. At lunch 7．have a good time__________ 8. Twice a week
- 6. The first grade of junior high school, First grade English evaluation manual with the answer of Unit2, good words give him 100 points!
- 7. Ask a problem of linear equation of one variable! If the order of three or three digits is reversed, the sum of the three digits is 1771
- 8. Mathematical master to solve (equation of one variable and one degree) A middle school requires students to build their own playground. It takes 7.5 hours to do it alone on the first day of junior high school; it takes 5 hours to complete it alone on the second day of junior high school? I've given you all my little fortune. I've written the title! I've got extra points in one hour!
- 9. Mathematics, solution of linear equation with one variable Since January 1, 2006, a city has implemented the rural cooperative medical system in an all-round way. Every farmer can enjoy the cooperative medical system with only 10 yuan each year. The following table shows the reimbursement rate of hospitalization expenses after the implementation of the rural cooperative medical system Reimbursement rate of hospitalization expenses (yuan) (%) The part not exceeding 3000 yuan 3000-4000 25 4000-5000 30 5000-10000 35 10000-20000 40 Over 20000 45 How many yuan did a person actually bear when he was hospitalized and reimbursed 805 yuan?
- 10. Help with math, The purchase price of a commodity is 3000 yuan and the price is 4500 yuan 1. The store requires a discount of no less than 5% of the profit. How much discount is the minimum? 2. If the market situation is not good, the store requires that the sales without loss be sold at a discount. How much discount is the minimum? 3. If there is a large stock of this product, the store requires a discount of no more than 5% of the price at a loss. How much discount is the minimum?
- 11. Put forward the question: according to the knowledge learned, eating fruits and vegetables often can prevent scurvy and enhance the body's immunity, because fresh fruits and vegetables are rich in vitamin C. but the nature of vitamin C is not stable enough, high temperature cooking, long-term storage and so on are easy to be damaged. As a common vegetable, can cucumber be eaten raw or cooked to make the human body absorb more vitamin C What about vitamin C? Make a hypothesis: your hypothesis:______ Make a plan: ① take two equal portions of cucumber, boil one portion of them, make juice respectively, and pour them into two small beakers. ② take two clean and dry small tubes No. 1 and No. 2, respectively, and inject 2ml of potassium permanganate solution of different concentrations, absorb the juice of raw cucumber with a dropper, and drop it into tube No. 1 drop by drop, while shaking and observing, until the color of potassium permanganate solution fades (3) then use the same dropper to absorb the juice of ripe cucumber, drop it into test tube No. 2, shake and observe the color of potassium permanganate solution until the color fades, and record the number of drops of juice (m)______ ．（2）______ Implementation plan: carry out the experiment according to the revised plan, count and analyze the experimental phenomena. Conclusion: Please predict the three experimental results and draw the corresponding conclusions (3)______ ．（4）______ ．（5）______ ．
- 12. Biology problems in grade one of junior high school Research on the experiment of "the influence of plants on air humidity" 1. Your question () 2. The hypothesis you made () 3. After comparing the air humidity of bare land, grassland and dense shrub, you know that the maximum air humidity is () and the minimum is () 4. Through inquiry, you come to the conclusion that () 5. Please refer to the relevant information and talk about the role of plants in improving our living environment? Solving++
- 13. Paramecium eat bacteria, so they are consumers and bacteria are decomposers. How to draw the food chain We can't start with bacteria, we can't start with Paramecium, because there are no decomposers in the food chain, and we have to start with producers
- 14. The food chain is formed by living things for the sake of other living things
- 15. The first volume of junior high school biology textbook content, urgent
- 16. A math problem in a textbook This is the fourth and eighth exercise of the sixth grade of pep Children's weight should not exceed 3 / 20 of their weight. If they carry heavy objects for a long time, it will cause low back pain and backache, and even hinder bone growth Wang Ming: weight 30kg, 5kg in the schoolbag (1) Is Wang Ming's schoolbag overweight? Why? (2) Weigh your weight and figure out how many kilograms you'd better not carry. (I can't do this.) my weight is 35kg
- 17. East China Normal University Press first volume mathematics book mathematics problems! (East China Normal University Press) the answer to question 25 on page 84 of the first volume of junior high school mathematics book? There is a picture 1+3+5+7+9+11＝（）² From this we can guess that the sum of N consecutive odd numbers from the beginning is equal to? ……
- 18. 2010 Haidian District junior high school mathematics final exam?
- 19. Explain 3B's Square = 9b's Square with geometric figure
- 20. 113 faces (1-6) The track of the sports ground is 400m long. A practices cycling, with an average of 350m per minute; B practices running, with an average of 250m per minute. How long has it taken for the two people to meet for the first time from the same place and in the opposite direction at the same time? How much time did it take to meet again?