![](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>)
On the pursuit of the equations in the seventh grade
First of all, draw two line segments, one represents the pursuer, and the other represents being pursued. Focus on the given distance, time, speed, and a series of keywords, and remember that the distance is equal to time multiplied by speed. And set up equations with the given keywords. Then some basic problems will be solved
What is the calculation formula of tax and after tax interest?
Tax = principal * interest rate * tax rate
After tax interest = principal * interest rate - principal * interest rate * tax rate
The calculation formula of area and volume is expressed by letters
Square area = side length multiplied by side length, s-positive = A & # 178; rectangle area = length multiplied by width, s-long = AB; square volume = edge length & # 179, v-positive = A & # 179; rectangle volume = length multiplied by width multiplied by height, v-long = ABH, circle area = π multiplied by radius, s-circle = π R & # 178; cylinder surface area = side area + two bottom areas, s-cylinder = s-side + 2S bottom area
To find the area formula of the ring, we should also use letters
It's urgent
S-ring = π (R & # 178; - R & # 178;)
There are two formulas for the area of a ring
(1) S-ring = π (R & # 178; - R & # 178;)
(2) Let the radius of the big circle be r and the radius of the small circle be r
Then the ring area = π R & # 178; - π R & # 178; s ring = s outer ring s inner ring
=πR² - πr²
Hope to help you, thank you!
Circle area formula
You can think of a circle as a big circle and a small circle. A circle is the area from the small circle to the big circle
The area of the big circle is the radius of the big circle multiplied by the radius and then multiplied by 3.14, the radius of the small circle is the radius of the small circle multiplied by the radius of the small circle to form 3.14, and the area of the big circle reduced by the area of the circle is the area of the ring
Definition of literal expression by multiplicative distributive law
Multiplicative distributive law
Two numbers are added (or subtracted) and multiplied by another number, which is equal to multiplying the number with two addends (subtracted) respectively, and then adding (subtracting) the two products to get the same number. It is indicated by letters: (a + b) x C = AXC + bxc. There is another expression: a (B + C) = AB + AC
What is the formula of multiplicative distribution law?
Formula:
Inverse operation:
a(b+c)=ab+ac
A simple chemical expression!
1. Mercury + oxygen → mercuric oxide 2. Mercuric oxide → mercury + oxygen → what are they filled in respectively? Do they all write heating? Or is the first one ignited and the second heating? Write silently tomorrow!
It's all heating
What is the difference between literal expression and symbolic expression
The literal expression is the expression of chemical reaction and reaction conditions in Chinese characters, such as sulfur combustion: sulfur + oxygen → sulfur dioxide (write "ignite" above the arrow)
The symbolic expression is the chemical formula to express the chemical reaction. S + O2 → SO2 (write the word "ignite" above the arrow)
On the basis of the symbolic expression balance, the arrow to equal sign, is the chemical equation
RELATED INFORMATIONS
- 1. A batch of saplings will be planted. If each person plants 10 saplings, the remaining 6 saplings will not be planted. If each person plants 12 saplings, the remaining 6 saplings will be missing. How many people plant trees? List the equations according to the meaning of the question
- 2. Solving problems by solving equations 1. There are 874 seats in the school auditorium, with a total of 23 rows. Each row has the same number of seats. How many seats are there in each row?
- 3. Write a composition about saving water, use the statistical knowledge learned in math class! In ten minutes,
- 4. Who has a good way to learn mathematics
- 5. The story of using mathematical knowledge in life Quality and quantity
- 6. Life examples solved with mathematical knowledge The best way to solve life problems with mathematical knowledge is at the level of junior high school,
- 7. Mathematical diary about decimal division (about 200 words), mathematical diary about polygon area (about 260 words)
- 8. Mathematics diary about 300 words in Grade Four
- 9. This is a question about comparison The length ratio of the three sides of a triangle is 3:4:5. The shortest side is 3 cm. What is the longest side of the triangle?
- 10. The formula of cylinder volume The formula of volume and area of cylinder and cone
- 11. In junior high school, the principle of common factor is put forward, 1. Decomposition common factor: 2x (A-2) + 3Y (2-A) 2. The common factor of polynomial A & # 178; - 2Ab + B & # 178;, a & # 178; - B & # 178; is (?) 3. Given X & # 178; + X-1 = 0, find the value of the cubic power of X + 2x & # 178; + 1999
- 12. Chemical formula and literal expression of carbon dioxide produced by reaction of calcium carbonate and dilute hydrochloric acid?
- 13. Is chemical equation literal expression or symbolic expression
- 14. The chemical equation of the symbolic expression of the reaction equation of copper heated in air
- 15. Write a literal expression of the chemical reaction that meets the following requirements 1. Formation of a combination reaction which can make the clarified lime water turbid 2. In the product, there is a decomposition reaction of the amount gas which can make the wood strip with Mars reburning （1）（2） 3. Formation of colorless and pungent chemical reactions 4. Formation of black solid 5. The combination reaction that produces a lot of white smoke 6. It is neither a combination reaction nor a decomposition reaction 7. It's just an oxidation reaction, but not a combination reaction 8. Intense combustion, produce dazzling white light reaction
- 16. Write down the following chemical reactions (1) Light yellow solid combustion_____________________________________________ (2) Preparation of oxygen by heating pure substance in laboratory_____________________________________________ (3) Heated light green powder_____________________________________________ (4) A metal burns in air_____________________________________________ (5) Reaction of producing colorless and odorless gas after combustion_________________________________________
- 17. Find a regular expression to judge whether the nicknames are letters, numbers, underscores and Chinese characters, and the length cannot exceed 16
- 18. The canteen bought some flour. On the first day, they ate half of the whole flour, which was less than 28 kg. On the second day, they ate the remaining half, which was less than 8 kg. Finally, they had 122 kg. How many kg of flour are there?
- 19. Circumference formula and area formula of semicircle fast
- 20. A few math problems of grade one in junior high school· The value of (x + y) ^ 3 (2x + 2Y) ^ 3 (3x + 3Y) ^ 3? 10 ^ α = 20, 10 ^ β = 5 ^ - 1, then the value of 9 ^ α / 3 ^ 2 β is?