Car a and car B run from a and B at the same time. Car a runs 56 kilometers per hour and car B runs 48 kilometers per hour. The two cars meet at 32 kilometers from the midpoint. How many kilometers is the distance between a and B?

A: the distance between a and B is 832 km

A problem of basic inequality of mathematics in grade one of senior high school!
It is known that a > = 3
Verification: radical a-radical (A-1) < radical (A-2) - radical (A-3)

A + √ (A-3) = 3, the square of √ (A-3) = A-3, the square of (√ A-2) = A-2, the square of √ (A-1) = A-1, and the square of √ a = A. (that is, the square of the number under the root sign is still a positive number.)
a+2√[a(a-3)]+a-3

A and B start from AB and go opposite each other at the same time. The speed of a is 80% of that of B. four hours later, they meet 40 kilometers away from the midpoint,
How many kilometers is the distance between a and B?

Suppose the distance between a and B is s km
(s/2 - 40) / (s/2 + 40) = 4 / 5
5(s/2 - 40) = 4(s/2 + 40)
2.5s - 200 = 2s + 160
0.5s = 360
X = 720 km

(2010. Zhengzhou three module) known vector a = (3, 4), B = (2, 1), if vector a+xb is perpendicular to B, then the value of X is ().
A. 233B. 323C. 2D. −25

∵ a = (3,4), B = (2, − 1) ∵ a + XB = (3 + 2x, 4-x), − B = (- 2,1) and ∵ a + XB is perpendicular to − B ∵ (3 + 2x) · (- 2) + (4-x) × 1 = 0, the solution is x = − 25, so D is selected

For two baskets of apples with the same kilogram, a sells 7 kilogram, B sells 19 kilogram, and the remaining kilogram in basket a is three times of that in basket B. how much of the two baskets?
Don't use equations,

A sells 7kg, B sells 19kg, and the remaining kilogram in basket a is more than that in basket B: 19-7 = 12kg
The difference multiple relation is as follows
Now B is: 12 / (3-1) = 6 kg
So, it turns out: 6 + 19 = 25 kg

Directional derivative of function r = radical (x ^ 2 + y ^ 2) along vector L = Xi + YJ
It's better to bring instructions

R is partial derivative of X: X / sqrt (x ^ 2 + y ^ 2)
Partial derivation of R for Y: Y / sqrt (x ^ 2 + y ^ 2)
The unit vector l0 of L = {x, y} * (1 / sqrt (x ^ 2 + y ^ 2))
The directional derivative = x ^ 2 + y ^ 2

It is known that 100 tons of cement can be transferred out from warehouse A, 80 tons can be transferred out from warehouse B, 70 tons from a and 110 tons from B. the distance and freight from two warehouses to ab are as follows:
Journey freight
Party A and Party B
a 20 15 12 12
b 25 20 10 8
If you want the freight to be 37400 yuan, please design the transportation plan

First of all, let a transport x tons to a, then B transport 70-x tons to a, a transport 100-x to B, B transport 10 + X tons to B, as follows:
Party A and Party B
a.x.70-x
b.100-x.10+x
20*12x+15*12(70-x)+25*10(100-x)+20*8(10+x)=37400
Find out X and bring it into the table, which is the transportation plan

In the triangle ABC, ABC is the opposite side of the angle. Let f (x) = a, T - (a-b) × t-4c. If f (2) = 0, then the range of angle c is

Because f (x) is the result of (f (x) (f (x) = a-t-178; X \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\35;178; - 2Ab * COSC = 2C & #178; - 2Ab * COSC

Car a can travel 20 kilometers in 28 minutes, and car B can travel 25 kilometers in 40 minutes. How fast is it per minute?

A: 20km / 28 ≈ 0.714km/min
B: 25km / 40 = 0.625km/min
089km / min faster than that of B

1、 Fill in the blanks
There are two students in each row, three students in each row, and two students in each row. There are no more than 150 students in the sixth grade
2. The fourth grade planted 130 trees on the tree planting day, which is less than two times of the third grade index. Then 130 - (130 + x) △ 2 stands for ()
3. The number of male students in class one of grade five is five sixths of that of female students. The number of female students accounts for () of the whole class. The number of male students accounts for () of the whole class. The number of male students is less than that of female students
4. For the two pools a and B, the original water storage of Pool B is one sixth less than that of pool A. now three fifths of the water stored in pool a is injected into pool B, and then 31m & sup3; of water is pumped from pool B. the water volume in the two pools is exactly the same. There is () cubic meters of water in pool B
1. The taxi charge standard of a city is 5 yuan for the first 3 km, and 1 yuan for every 0.5 km for more than 3000 m
Δ Xiao Gang came back from the design institute by taxi and spent 15.5 yuan. How many kilometers did he drive by taxi?
2. There are 100 tourists queuing in front of the world historical and Cultural Heritage Museum of terracotta warriors and horses. The number of tourists per minute after opening is equal. One entrance can accommodate 10 tourists per minute. If two entrances are opened for 20 minutes, all tickets can be checked, and no one is queuing outside. In order to reduce the queuing time of tourists, four entrances are now opened, So how many minutes after the door opened, there was no one in line?

1、 Fill in the blanks
There are two students in each row, three students in each row, and two students in each row. There are no more than 150 students in the sixth grade
2. The fourth grade planted 130 trees on the tree planting day, which is less than two times of the third grade index. Then 130 - (130 + x) △ 2 stands for ()
3. The number of male students in class one of grade five is five sixths of that of female students. The number of female students accounts for () of the whole class. The number of male students accounts for () of the whole class. The number of male students is less than that of female students
4. For the two pools a and B, the original water storage of Pool B is one sixth less than that of pool A. now three fifths of the water stored in pool a is injected into pool B, and then 31m & sup3; of water is pumped from pool B. the water volume in the two pools is exactly the same. There is () cubic meters of water in pool B
2、 Solve the problem
1. The taxi charge standard of a city is 5 yuan for the first 3 km, and 1 yuan for every 0.5 km for more than 3000 m
Δ Xiao Gang came back from the design institute by taxi and spent 15.5 yuan. How many kilometers did he drive by taxi?
(15.5-5)×0.5+3=8.25
2. There are 100 tourists queuing in front of the world historical and Cultural Heritage Museum of terracotta warriors and horses. The number of tourists is equal every minute after the opening of the museum. There are 10 tourists at one entrance. If two entrances are opened for 20 minutes, all tickets can be checked, and there is no queue outside. In order to reduce the queuing time of tourists, now four entrances are opened, how many minutes after the opening of the museum, no one will queue up?
Two entrances can accommodate 20 × 10 × 2 = 400 tourists in 20 minutes
New visitors per minute (400-100) △ 20 = 15
Four entrances can accommodate 10 × 4 = 40 visitors per minute
In addition to 15 new comers per minute, 40-15 = 25 can be added
It takes 100 △ 25 = 4 minutes to put all 100 people in
Comprehensive formula: 100 △ 10 × 4 - (20 × 10 × 2-100) △ 20]

Car a and car B run from a and B at the same time. Car a runs 56 kilometers per hour and car B runs 48 kilometers per hour. The two cars meet at 32 kilometers from the midpoint. How many kilometers is the distance between a and B?