Given that the mean of a sample m, 4,2,5,3 is n, and M + n = 4, then the variance of the sample is () solve equations 1 + 2 of X + 1 = 2x + 2 of X
The variance is 2
To solve the equation, you multiply (x + 1) (x -)
In this way, it becomes a linear equation of one variable, which is easy to solve
Don't forget to verify it in the end
If = 0 in the value of X (x + 1) (x-1) is an increasing root, it must be rounded off
So this equation has no solution
If it is not equal to 0, the value obtained is the solution of the original equation
Almost all fractional equations are solved in this way
RELATED INFORMATIONS
- 1. What are the square root and the square root of the second power arithmetic of (- 4 / 13) The fourth power of minus thirteen Arithmetic square root square root
- 2. As shown in the figure, in rectangular ABCD, AC and BD intersect at point O, AE bisects ∠ bad, BC intersects at E. if ∠ EAO = 15 °, then the degree of ∠ BOE is______ Degree
- 3. 1. Given x + 1 / x = 4, then the value of X & sup2; + 1 / X & sup2; is () A. 12 b.1/2 c.16 D. uncertain 2. Given x = 2009, y = 2010, then (x + y) · X & sup2; + Y & sup2 / / X quartic - y quartic equals () 3. If x / 3 = Y / 4 = Z / 7, then the value of 3x + y + Z / y is ()
- 4. A village wants to buy three kinds of trees. It is known that the price ratio of three kinds of trees is 2:2:3, and each tree is 200 yuan. Now it plans to use 210000 yuan to buy a total of 1000 trees If you buy tree a twice as much as tree B, and you just run out of money, how many trees can you buy If the purchase price of 10120 yuan is increased, how many trees can C buy at most on the premise that the total tree purchase remains unchanged?
- 5. First dissolve: (A & sup2; - B & sup2; / A & sup2; - AB) / A & sup2; + 2Ab + B & sup2; / A, when B = - 1, then from - 2
- 6. From the autumn of 2009 to May of this year, there was a serious drought in our city. From April 15 to 21 this year, both a and B middle schools had no water supply. The higher authorities immediately organized water supply activities, and each time they sent 7600 liters to a middle school and 4000 liters to B middle school. It is known that the per capita water supply is the same, the number of teachers and students in a middle school is two times that of B middle school, 20 less. (1) how many teachers and students are there in these two middle schools? (2) If you send bottled water, the price is 1 yuan / L; if you send drinking spring water by fire truck, you don't need to buy it, but you need to deliver water tower. The price of 500 liter water tower is 520 yuan / piece. Other expenses are ignored. Please calculate the cost of sending all bottled water or all drinking spring water by fire truck for the first time?
- 7. Nanxun ancient town is a famous tourist attraction in China. Here is a passage about the charging standard between a school team and a tour guide of a travel agency Leader: how much is the charge for a tour to Nanxun? Tour guide: if the number of people does not exceed 30, the per capita travel cost is 360 yuan Leader: if more than 30 people, how to get a discount? Tour guide: if there are more than 30 people, the per capita travel expenses will be reduced by 5 yuan for each additional person, but the per capita travel expenses shall not be less than 300 yuan (1) If a group of 20 people go on a tour, the school will give the total cost to the travel agency_____ Yuan (2) The school's travel agency charges a total of 12400 yuan to the travel agency after the end of the group tour, asking for the number of the school's tour to Nanxun; 2. In the plane rectangular coordinate system, take points a, B, C and D as vertices to form a parallelogram, where points a (2, N + 1), B (n-1, N + 4) and C (- 5-N, N + 5) are all on the same inverse scale function image, then n=____ The coordinates of vertex D are____ .
- 8. A meteorological research center observed the whole process of a sandstorm from its occurrence to its end. At the beginning, the wind speed increased by 2km / h on average. After 4h, the wind speed increased by 4km / h on average when the sandstorm passed through the open desert. For a period of time, the wind speed remained unchanged at 32km / h. When the sandstorm met the green vegetation area, the wind speed decreased by 1km / h on average. At 40H, the measured wind speed was 17km / h According to the images of wind speed and time, the following questions are answered: (1) fill in the corresponding values in the y-axis (); (2) how many hours have the sandstorm passed from the occurrence to the end? (3) The functional relationship between wind speed y (km / h) and time x (H) is obtained when x ≥ 4
- 9. Given that the side length of square ABCD is 8, point m is on DC, DM is 2, and N is the first moving point on AC, then the minimum value of DN + Mn is? I know it's 10, but how can I get it? It's better to have a picture Also, I wish you a happy New Year's Day!
- 10. There is a triangular open space in the campus. Now we are going to plant turf on this open space to beautify the environment. We have measured its three side lengths of 13 meters, 14 meters and 15 meters respectively. If the price of this kind of turf is 120 yuan per square meter, how much will it cost to buy this kind of turf at least? So what? It's better to be complete
- 11. Exercises of equations in the second volume of junior high school mathematics
- 12. Exercise 2 on page 54 of mathematics volume 2 of junior high school
- 13. Exercises in volume two of junior high school mathematics The electric maintenance workers of the power supply bureau had to go to the suburb of 30 kilometers for electric maintenance. The maintenance workers left first by motorcycle. After 15 minutes, the repair car loaded with the required materials set out. As a result, they arrived at the same time. The speed of the repair car was 1.5 times that of the motorcycle. The speed of two kinds of cars was calculated 2. The total length of the expressway between a and B is 200 kilometers, which is 20 kilometers less than the original national highway. After the expressway was opened to traffic, the driving speed of a long-distance bus was increased by 45 kilometers per hour, and the driving time from a to B was shortened by half. The speed of the long-distance bus on the original national highway was calculated
- 14. There is a large oil tank in an oil depot. In the first 8 minutes, only the oil inlet pipe is opened but not the oil outlet pipe. When the oil in the oil tank reaches 24 tons (there is no oil in the crude oil tank), the oil inlet pipe and the oil outlet pipe are opened simultaneously for 16 minutes. The oil in the oil tank increases from 24 tons to 40 tons. Then the oil inlet pipe is closed and only the oil outlet pipe is opened until all the oil is discharged, It is assumed that the flow rates of the inlet pipe and the outlet pipe remain constant respectively in unit time Write the functional relationship between the oil storage quantity Q (ton) and the time t (minute) of oil in and out in this period
- 15. Boss Li, a fruit seller, sells a kind of high-grade fruit. If he makes a profit of 10 yuan per kilogram, he can sell 500 kg per day. According to the market survey, if the price of the imported fruit remains unchanged, if the price of the imported fruit increases by 1 yuan per kilogram, the daily sales volume will decrease by 20 kg. Now boss Li wants to make a profit of 6000 yuan per day and at the same time make the customers get benefits. How much yuan should the price of the fruit increase per kilogram I know the equation is (10 + x) x (500-20x) = 6000 But can you give me a detailed analysis, why do you want to do this, what does 10 + X Stand for What does 500-20x stand for What does 20x stand for? Why multiply 20kg by the price increase
- 16. It is known that A-B = 2, (A-1) (b-2) < ab (1) Find the value range of A; (2) If a & sup2; + 2Ab + A + B & sup2; - B = 38, find the value of a + B Clear steps are required
- 17. Seek the master to solve the mathematics problem of the second grade of junior high school Xiao Li bought a kilogram of nugan watermelon in the market at the price of 0.8 yuan per kilogram and sold it in the market. After selling some of the watermelons, all the watermelons were sold out at a price of 0.4 yuan. The relationship between the sales and the kilogram of melons is shown in the figure. Xiao Li just got the solution on QQ and bought a total of 50kg watermelons. The first 40kg sold for 1.6 yuan, and the last 10kg sold for 1.2 yuan The revenue is 76-64 = 12 / 1.2 = 10, that is, 10kg, which is mainly not shown on Baidu 40 + 10 = 50kg 0.8*40+0.4*10 36 yuan
- 18. [1]1,3,7,13,21. Note that the functional relation between the nth number and N is [] [2] If the average of the first five numbers is 8 and the average of the last five numbers is 10, then the median of the nine numbers is []
- 19. Write any three digit number to meet the following requirements: 1. The number of hundred is larger than that of one 2. Exchange hundreds and ones, and subtract decimals from large numbers 3. Exchange the hundreds and individual digits of the difference, and add with the difference between the large number and the decimal It turns out to be 1089 every time. Why?
- 20. (square of 2 + 1) (4th power of 2 + 1) (8th power of 2 + 1) (16th power of 2 + 1) =?