![](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>)
The light from the flashlight gives us () A. Straight line B. ray C. line segment D. broken line
The light emitted by the flashlight gives us the feeling that the flashlight is the end point of the ray, and the direction of light propagation is the direction of the ray, so it gives us the feeling that it is a ray
The sum of all terms of sequence 81, - 27,9, - 3
(1) The sum of all terms of sequence 64,16,4,1
(2) The sum of all terms of sequence 81, - 27,9,3 -
It's a process!
By the way, there is a process must add points!
(1)
an=4^(4-n)=16/4^n
A (n + 1) / an = 4 ^ n / 4 ^ (n + 1) = 1 / 4, the first term A1 = 64, not equal to 0, the sequence is equal ratio sequence
Sn=64*[1-(1/4)^n]/(1-1/4)=(256/3)(4^n-1)/(4^n)=256/3-256/(3*4^n)
When n tends to infinity, 256 / (3 * 4 ^ n) tends to zero
Sn limit = 256 / 3
(2)
A (n + 1) = an * (- 1 / 3), the first item 81 is not equal to 0, and the sequence is equal ratio sequence
Sn=81*[1-(-1/3)^n]/(1-1/3)=(243/2)[(3^n-1)/3^n]=243/2-243/(2*3^n)
When n tends to infinity, 243 / (2 * 3 ^ n) tends to zero
Sn limit = 243 / 2
The two questions are of the same type
-The square of X + the third power of X-2, the highest power term is? 2, the coefficient is? And the constant term is?
-The square of X + the third power of X-2, the highest power term is the square of - x, the coefficient of the second power term is the square of - x, and the constant term is - 8
The application of the first degree equation of one variable in junior high school mathematics
The distance between a and B is 162 kilometers. A slow train leaves from a station and walks 48 kilometers per hour, while an express train leaves from B station and walks 60 kilometers per hour. How long can two trains meet each other when they are facing each other at the same time
2) The two cars were going in the opposite direction at the same time. A few hours later, they were 270 kilometers apart
3) If the two cars are facing each other, how long will it take for the local train to leave for one hour
Only two cars can meet
4) If the two cars are facing each other, the express will drive for 25 minutes first, and the express will drive for several hours
Meet the local train
5) The two trains are going in the same direction at the same time (the express is at the back), and the express will run in a few hours
You can catch up with the local train
6) The two cars are going in the same direction at the same time (the local train is at the back). After a few hours, the two cars meet
200 km away
7) How long does it take for the two trains to run in opposite directions at the same time?
1. If we meet after X hours, then 48x + 60x = 162
2. If the distance between two vehicles is 270 km after X hours, then 48x + 60x = 270-162
3. If we meet after X hours, then 48x + 60x = 162-48
4. If the express train meets the local train for another x hours, then 48x + 60x = 162-1 / 4 * 60
5. If the fast train can catch up with the slow train after X hours, then 60x = 48x + 162
6. If the distance between two vehicles is 200 km after X hours, then 60x-48x = 200-162
The famous venbonacci sequence is as follows: 1, 1, 2, 3, 5, 8, 13, 21 What is the remainder of the 2010 number divided by 3
There is a string of numbers 1, 1, 2, 3, 5, 8 Starting from the third number, each number is the sum of the first two numbers. Among the first 2009 numbers in this series, are there --- multiples of 5?
At present, there are 254 candies, 210 biscuits and 186 oranges. There are more than 40 people in the large class of a kindergarten. Everyone gets the same amount of candies, biscuits and oranges. The ratio of the remaining candies, biscuits and oranges is 1:3:2. There are more than 40 people in the large class_____ Each child gets candy_____ Biscuits, biscuits_____ Pieces, oranges_____ One
The remainder of venbonacci sequence divided by 3 has the following rule
1、1、2、0、2、2、1、0、
1、1、2、0、2、2、1、0、
---------
2010÷8=251-----2
The remainder 1 is obtained by dividing the number 2010 by 3
Good luck
There is a string of numbers 1, 1, 2, 3, 5, 8 Starting from the third number, each number is the sum of the first two numbers. Among the first 2009 numbers in this series, are there --- multiples of 5?
The individual number of venbonacci sequence has the following rule
1、1、2、3、5、8、3、1、4、5、
9、4、3、7、0、7、7、4、1、5、
-----------
There are two multiples of five in every ten numbers, or one multiples of five in every five numbers
There are 401 multiples of 5 in the first 2009
At present, there are 254 candies, 210 biscuits and 186 oranges. There are more than 40 people in the large class of a kindergarten. Everyone gets the same amount of candies, biscuits and oranges. The ratio of the remaining candies, biscuits and oranges is 1:3:2, and the large class has 40___ 46__ Each child gets candy__ 5___ Biscuits, biscuits_ 3____ Pieces, oranges__ 3___ One
Good luck
It is known that a, B and C are three sides of a triangle respectively. It is proved that a square minus b square minus C square minus 2Ac is greater than 0
Which expression of "a square minus b square minus C square minus 2Ac greater than 0" is not clear, is a ^ 2-B ^ 2-C ^ 2-2ac > 0 or a ^ 2 - (b ^ 2-C ^ 2-2ac) > 0?
If it is the former, there are counter examples to illustrate the error
If it is the latter, it can be proved as follows:
Since a, B and C are the three sides of the triangle, a + C > b, so (a + C) ^ 2 > b ^ 2, that is to say
a^2-(b^2-c^2-2ac)>0.
Summary of 2-1 knowledge points of mathematics PEP elective course
Commonly used logic terms, space vector and solid geometry, conic curve and equation. Such a big project has no bonus points? Then I can only deal with it casually. How much time does it take to talk about it all? I study hard. Only what I summarize is my own. What others tell you is not wine and meat, but there is no real thing left
The number of red balls is 3 / 4 of the number of white balls, and the number of white balls is 4 / 3 of the number of red balls. What is the proportion of the number of white balls in the total number of the two kinds of balls?
Let the white ball be the unit "1", because the number of red balls is 3 / 4 of the number of white balls,
So the number of red balls is 3 / 4, and the total number of red balls is 1 + 3 / 4 = 7 / 4
The number of white balls accounts for 1 / (7 / 4) = 4 / 7 of the total number of two kinds of balls
How much is 1 ml
Algebraic
1ml=0.001l
Average score of Chinese mathematics 96 average score of mathematics foreign language 94 average score of Chinese foreign language 95 three scores?
Don't make it clear
In the mid-term exam, the average score of Chinese and mathematics is 96, the average score of mathematics and foreign language is 94, and the average score of Chinese and foreign language is 92
Because the average of this problem is the sum of two numbers divided by two
Chinese + mathematics = 192
Mathematics + foreign language = 188
Chinese + foreign language = 184, so 192 + 188 + 184 = 564
Divided by 2 = 282 is Chinese + mathematics + foreign language
So Chinese = 282-188 = 94
Math = 282-184 = 98
Foreign language = 282-192 = 90
RELATED INFORMATIONS
- 1. For three consecutive even numbers, if the sum of squares of the first two numbers is less than 4, then the three numbers are
- 2. How to calculate simply by 8 times bracket, 125 times 9 times bracket
- 3. Please help me When an engineering team is bidding, it receives the bidding documents from engineering teams a and B There are three options: 1. Team a works alone, just on schedule; 2. Team B works alone, 5 days more than the specified time limit; 3. If team a and team B cooperate for 4 days, the rest of the project will be completed by team B alone, just on schedule Q: how many days will it take for team a and team B to complete the project separately? I want to write out the complete steps,
- 4. When the length and width of a rectangle are expanded three times at the same time, the perimeter is 72 cm. What is the original perimeter of a rectangle? Who knows the answer, When the length and width of a rectangle are expanded three times at the same time, the perimeter is 72 cm. What is the perimeter of the original rectangle?
- 5. It is known that a × 3 and 1 / 3 = 12 / 11 × B = 5 / 15 × C, and a, B, C are not equal to zero. A, B, C are arranged according to the size, and the reasons are given
- 6. Let x ∈ [1100] find the range of y = x ^ (1-lgx)
- 7. One hundred small squares with a side length of one centimeter are used to make a large square, and the area of the large square is one
- 8. A round fountain with a radius of 20 meters. Now we need to build a 1-meter-wide path around the fountain. The path covers an area of 20 meters
- 9. The average of x1.x2.x3.x4. The average of X1 + 3.x2 + 3.x3 + 3.x4 + 3
- 10. Let ∑ be the plane x + y + Z = 1, then ∫ 2 / (x + y + Z) DS is equal to?
- 11. An area of 560 square meters of green space, increase the width from 8 meters to 24 meters, the length of the same. After the expansion of the green area is how much?
- 12. 1+2+3+4+5+6+7+8+9+.1000+.10000+.10000
- 13. If the relative acceleration between objects is zero, there must be static friction between two objects
- 14. F (x) = ln (1 + x), when x →?, f (x) is infinitesimal Such as the title Thank you very much!
- 15. Which is the smallest of 9 out of 13, 16 out of 48 and 45 out of 50 I'm tired of it. I hope you can help me
- 16. Y = f (sin ^ 2 (3x)),
- 17. What is the speed of light and sound
- 18. 45 = () x () x () prime in brackets
- 19. Prime number 30 = () + () = () + () = () + () () = () + () () = () + () = () + ()
- 20. 91 = () times () prime