Define a new operation: m # n = Mn + m + N, then 1 # 2 # 3 #How many different calculation results can be obtained by adding several pairs of brackets to 10?

A total of 46 different results can be obtained

From a to B, it takes 10 hours for a bus and 15 hours for a train. The two trains leave from the two cities at the same time. When they meet, the bus is just 240 kilometers away. How much is the distance between a and B

It is known that it takes 10 hours for a bus and 15 hours for a train to go from a to B. suppose the speed of the bus is a and the speed of the train is B. because the distance from a to B is the same, 10a = 15b, a = 1.5b, that is, the speed of the bus is 1.5 times that of the train
It takes the same time for the two cars to set out at the same time to meet. The bus has traveled 240 kilometers, which is 1.5 times of the distance of the train. Therefore, dividing 240 by 1.5 gives 160 kilometers, which is the distance of the train
240+160=400km
The distance between the two cities is 400 kilometers

1/（123）+1/（234）+1/（345）…… +How to calculate 1 / (8 * 9 * 10)

Solution: a (n) = 1 / N (n + 1) (n + 2) = 0.5 [1 / N (n + 1)] - 0.5 [1 / (n + 1) (n + 2)] for the sequence B (n) = 0.5 / N (n + 1), split term summation method can be adopted: S1 (n) = 0.5 [1 - (1 / 2) + (1 / 2) - (1 / 3) +. + (1 / N) - 1 / (n + 1)] = 0.5 [1-1 / (n + 1)] = 0.5N / (n + 1) for the sequence C (n) = 0.5 / (n + 1) (n + 2), Using the same method, we get: S2 (n) = S1 (n + 1) - B (1) = 0.5 (n + 1) / (n + 2) - 0.25, so there are the first n terms of the original sequence and: s (n) = S1 (n) - S2 (n) = 0.5 [n / (n + 1) - (n + 1) / (n + 2) + 0.5] original formula = s (8) = 0.5 [(8 / 9) - (9 / 10) + 0.5] = 11 / 45

The speed of a jet plane is 1.5 times the speed of sound. It flies at an altitude of 2720m in horizontal direction. When you hear the plane roaring overhead, look up and see how far the plane has gone in front of you?

(1) According to the meaning of the question, the speed of the plane: v = 1.5V sound = 1.5 × 340m / S = 510m / S; (2) the time of the sound from the plane to the human ear: T = HV sound = 2720m340m / S = 8s, & nbsp; the distance of the plane: S = VT = 510m / s × 8s = 4080m; a: look up, the plane has reached the level of 4080m in front of you

Three times of a number minus four halves, the difference is five, find the number. (equation)

Let this number be X
3X-4*1/2=5
3X-2=5
3X=7
X=7/3

Is friction related to contact area
Explain~
1. I have done an experiment, that is, there are two books, and each book is divided into two parts. It is easy to open the two books by clamping them together and pulling them apart. But if we clamp the two books page by page and pull them again, it is difficult to open or even unable to open them. What is the reason
2. Wind the rope around the stick or stake for several times, and it can be tied without tying. The principle is "the size of friction is related to the pressure" or "the size of friction is related to the contact area"
Can you give me an example or experiment to prove "whether the size of friction force is related to the area"? If you can't give me an example, you can tell me the conclusion. Before that, I checked. Some people like to say "the size of friction force is related to the area within a certain range." if so, how large is the range? Can you give me an example~
Thank you, thank you, hard work, hard work, trouble, trouble, please, please
thank you!

For two separate books, f = MGU (U is the coefficient of friction), but if there is a pair of clips, each contact surface will have its own friction. If the book has 100 pages, there are 398 friction forces (the top and bottom covers are not forced), which can be calculated by F = nu (list the formula

If a and B are fixed values and (2kA) △ 3 - (x-bx) △ 6 = 2, no matter what the value of K is, his solution is always x = 1, so we can find the values of a and B

(2ka)÷3-(x-bx)÷6=2
Bring in x = 1
(2ka)÷3-(1-b)÷6=2
(2ka)/3+(b-1)/6=2
4ka+b-1=12
4ka+b=13
a=0 b=13

The car and the bus leave from the two stations at the same time. The car travels 82 kilometers per hour, and the bus travels 68 kilometers per hour. When the two cars meet, the car will not leave
35 kilometers more than the bus. How many hours did the two cars travel when they met? How many kilometers is the distance between the two stations?
Use x, not XY

It took x hours
82X-68X=35
14X=35
X=35/14
X=2.5
It took 2.5 hours to meet
Distance = 2.5 × (82 + 68) = 375 km

If (6-1) has a small 2 + | B + 1 | = 0, what is the value of 2007 + B and 2008?
Find the value of a + B by knowing that there is a 2 = a | B | = 4 on a head
.

The square of (A-1) + | B + 1 | = 0
Then A-1 = 0, B + 1 = 0
a=1,b=-1
therefore
2007 power of a + 2008 power of B
=2007 power of 1 + 2008 power of (- 1)
=1+1
=2

Given x = 1 / 2, y = 1 / 3, find the value of (2x + 3Y) &# 178; - (2x-3y) &# 178

（2x+3y）²-（2x-3y）²
=（2x+3y+2x-3y）（2x+3y-2x+3y）
=24xy
=24×1/2×1/3
=4

Define a new operation: m # n = Mn + m + N, then 1 # 2 # 3 #How many different calculation results can be obtained by adding several pairs of brackets to 10?