Four out of nine tons can be regarded as one ton (), or four tons ()

Four out of nine tons can be regarded as one ton (), or four tons ()

4/9
1/9

1 8 27 64 () () fill in the number according to the rule

1 8 27 64 125 216
analysis:
The third power of 1 = 1
The third power of 2 = 8
The third power of 3 = 27
The third power of 4 = 64
The third power of 5 = 125
The third power of 6 = 216

X + y = 7, xy = 10, find the value of X-Y

（X+Y）²=49=X²+Y²+2XY
（X-Y）²=X²+Y²-2XY
Then (X-Y) &# 178; = (x + y) &# 178; - 4xy = 49-10 = 9
Because I don't know which X or Y is bigger or smaller
Then X-Y = ± 3
This is a general method, even if you can't work out the values of X and Y like upstairs

In our daily life, people use the reflection of light to solve problems. This paper gives some examples and explains how to use the reflection principle of light

Submarine lookout mirror - the light refracts from the first mirror to the second mirror at the corner, so that people can see the appearance on the water. Fire - aim a magnifying glass at the light source and shredded paper. It is used for imaging - the luminous body is placed in front of the spherical mirror, and the light can also be imaged through the reflection of the spherical mirror; this is the same as the reflection imaging of the plane mirror, But the situation is as like as two peas. The translucent mirror, which is exactly like the usual bronze mirror in ancient times, is also made of metal, with a pattern and character, and the reflector is very bright. It can be taken as a human. As a rule, when a light falls on the mirror, it will be a bland round bright area after reflection. In this bright area, there is a pattern on the back of the mirror, which seems to be "transparent", so it is called "transparent mirror". In addition, there are car mirrors, doctor's forehead mirrors, laser reflectors, reflective telescopes (the common optical systems of reflective telescopes are Newton's and Cassegrain's), torches, and so on, Originally, the light of an electric bubble diffuses everywhere, and the scattered light is gathered together by reflection to form a beam

A group of √ 2 / 3, √ 6 / 3, √ 4 / 9,2 / 3, √ 8 / 27,2 √ 6 / 9 Write the 2N-1 and the 2nth number in the group

In the case of 2 / 3, 3 / 3 {2 / 3 \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ 3) n times

Let a be a matrix of order m × N and B be a matrix of order n × m. It is proved that if M > N, then the determinant | ab | = 0

Because R (AB)

Answers on page 27 of mathematics exercise book grade 7 Volume 1 (1)

Go to the bookstore and buy a special reference book for the classroom. There are answers to the exercises at the back. It's not that bad. It can solve many problems. That's how I dealt with my homework at the beginning

Arrange the positive and even numbers into 5 columns according to the following table
Column 1 column 2 column 3 column 4 column 5
Line 1 2 4 6 8
Line 2 16 14 12 10
Line 3 18 20 22 24
…… 28 26
According to the above arrangement, 2000 should be___ Yes___ Column
Better have a text explanation)
There's a little bit of a problem up there
Column 1 column 2 column 3 column 4 column 5
Line 1 2 4 6 8
Line 2 16 14 12 10
Line 3 18 20 22 24
…… 28 26

Then 2000 should be in the_ 500__ Yes_ 1__ Column

The factor of 15 is______ The multiple of 15 within 100 is______ ．

The factors of 15 are: 1, 3, 5, 15; the multiples of 15 within 100 are: 15, 30, 45, 60, 75, 90; so the answers are: 1, 3, 5, 15; 15, 30, 45, 60, 75, 90

It's better to use proportion instead of arithmetic!
1. The distance between a and B is 60 kilometers. A and B start from a to B at the same time. A takes a bus, B drives a car. The speed of a bus is 5 / 9 of that of a car, and B arrives 32 minutes earlier than a
2. The big ring and the small ring roll over the same length of the road. The circle number of the big ring is four fifths of that of the small ring. The circumference of the small ring is 44 cm shorter than that of the big ring. The big ring turns 60 times. How long is the road?
3. The mall opens at 9:30, and the employees arrive at 9:00. Aunt Wang goes to work in the mall in the morning. If the car speed is 150 m / min, she can arrive at the mall 10 minutes earlier; if the bicycle speed is 90 m / min, she can arrive at the mall 8 minutes earlier. How far is Aunt Wang's home from the mall? When did she start?

2 π (R-R) = 44 2 π R * 60 = 2 π R * 60 * 4 / 5 to solve