Divide both sides of the equation 3x = 2x by X to get 3 = 2. For the reason of the error, four students expressed the following opinion: A: "the equation itself is

Divide both sides of the equation 3x = 2x by X to get 3 = 2. For the reason of the error, four students expressed the following opinion: A: "the equation itself is

The reason for the error: when x = 0, you can't do divisor

When the square of equation 2x-3x-7 = 0, the resulting equation is

2x^2-3x-7=0
2(x^2-3x/2)-7=0
2(x^2-3x/2+9/16)-9/8-7=0
2(x-3/4)^2=9/8+7
(x-3/4)^2=65/16

If cos (x + y) = 1 / 5, cos (X-Y) = 3 / 5, then tanx.tany=?
Help me understand

cos(x+y)+cos(x-y)=2cos[(x+y+x-y)/2]cos[(x+y-x+y)/2]=2cosx*cosy=4/5
cos(x+y)-cos(x-y)=-2sin[(x+y+x-y)/2]sin[(x+y-x+y)/2]=-2sinx*siny=-2/5
cosx*cosy=2/5
sinx*siny=1/5
tanx.tany= (sinx*siny)/(cosx*cosy)=1/2

Put "+, -, ×, △" in the appropriate circle respectively (the operation symbol can only be used once), and fill in the appropriate number in the box
Let the following two equations hold
36○0○15=15 21○3○5=□

36×0+15=15 21÷3-5=2

What does the function image mean above the X axis

For any x, the function value Y > 0

The assembly group needs to assemble 200 bicycles, 92 of which have been assembled. If the remaining 9 bicycles are assembled every day, they can be assembled in X days
(1) Number of vehicles assembled______ ,______ ；
(2) Number of vehicles to be assembled______ ,_______ .
Buy 5 tables and a chair for M yuan. It is known that the price of each table is t yuan, and the price of each chair is 40 yuan. Write two formulas or quantities according to the following questions
The assembly group needs to assemble 200 bicycles, 92 of which have been assembled. If the remaining 9 bicycles are assembled every day, they can be assembled in X days
(1) How much does it cost to buy a table_______ ,_______ .
(2) The amount of money shared_______ ,_______ .

Number of vehicles assembled_ 92_ _ ,_ 200-9x_____ ；
Number of vehicles to be assembled_ 200-92_____ ,_ 9x______ .
）How much does it cost to buy a table_ 5t______ ,_ m-40a______ .
）The amount of money shared_ m______ ,5t+40a_______ .

Ellipse C: 3x ^ 2 + 4Y ^ 2 = 12, find the range of M, so that for the straight line y = 4x + m, C has two different points about l symmetry

Let P (x1, Y1), q (X2, Y2) be two points of symmetry on a straight line, and the equation of the straight line is y = - 1 / 4x + B, which is brought into the elliptic equation. It is sorted out that 13X ^ 2-8bx + 16b ^ 2-48 = 0, because X1 is not equal to X2, so △ > 0
Jiede radical 13 / 2

What is Kun Peng's Kun {flat tongue sound}

There's no topic. I'm too lazy. Children should study hard

Given that the equations of two circles are respectively x ^ 2 + y ^ 2-4x + 4Y = 0 and x ^ 2 + y ^ 2 + - X-1 = 0, then the line where the common chord of two circles lies

Subtracting 4y-3x + 1 = 0

Practical problems of decimal in Beijing Normal University Edition

1. The car travels 18 meters per second, the length of the car is 18 meters, and the length of the tunnel is 324 meters. How long does it take for the car to pass through the tunnel?
2. The highway from Shijiazhuang to Chengde is 546 kilometers long. When can the Honghong family drive from Shijiazhuang to Chengde to visit the summer resort? If they drive 78 kilometers per hour on average and leave at 8 am?
3. A bus starts from Zhangcun. If it travels 60 kilometers per hour, it can reach Lizhuang in 4 hours. As a result, it only takes 3 hours to get there. How many kilometers does the bus actually travel per hour?
4. An average train runs 71 kilometers per hour before the speed increase, 12 hours from Qinhuangdao to Handan, and 95 kilometers per hour after the speed increase. How many hours does it take from Qinhuangdao to Handan after the speed increase?
5. A long-distance bus from Beijing to Qingdao passes through Tianjin and Jinan. It leaves from Beijing at 6:30 in the morning, with an average of 85 kilometers per hour. When can it reach Qingdao?
It is 137km from Beijing to Tianjin, 360km from Tianjin to Jinan and 393km from Jinan to Qingdao
6. It's 936 kilometers from a to B, 216 kilometers in 3 hours for big cars, 1066 kilometers from a to B, 312 kilometers in 4 hours for small cars?
7. A car travels 60 kilometers per hour to and from a and B, and 40 kilometers per hour to and from B. find the average speed of the car
8. A student with 5km / h speed forward, can arrive at the school in time from home, after walking 1 / 3 of the whole journey, he took a bus with 20km / h speed, therefore, arrive at the school 2 hours earlier than the specified time, ask: how far is his home from the school?
9. A certain aircraft can fly in the air for 4 hours at most, the speed of flying out is 600 km / h, and the speed of flying back is 550 km / h. Q: how many kilometers can this aircraft fly out?
10. The two trains run on parallel tracks respectively. The length of the express train is 100 m, and that of the local train is 150 m. when the two trains run in opposite directions, it takes 5 s for the express train to pass a window of the local train
(1) The time taken for a slow train to pass a window of an express train when two trains are facing each other
(2) If two trains go in the same direction, the speed of the local train is 8m / s, and the fast train catches up with the local train from the back, then what is the time from the front of the fast train catching up with the rear of the local train to the rear of the fast train leaving the front of the local train?
11. One engineering team builds 85 meters of roads every day. According to this calculation, how many meters of roads do four engineering teams build in seven days?
12. The five workshops of the electric fan factory produce 2250 electric fans in 30 days. How many electric fans does each workshop produce per day? (check after answering)
13. Master Li processes 49 parts per hour, and master Zhang processes 54 parts per hour. They work for 8 hours each. How many less does Master Li do than Master Zhang?
14. The fruit shop brought 25 baskets of apples and pears, each of which is 6kg. The pears are 8kg. How many kilos are there in all?
15. In spring, 52 people went to the fifth grade to plant 26 trees per person; 48 people went to the fourth grade to plant 25 trees per person. How many more trees did the fifth grade plant than the fourth grade?