Why do astronauts in space sigh that "our earth is too lovely, but it's too easy to break at the same time?"

Why do astronauts in space sigh that "our earth is too lovely, but it's too easy to break at the same time?"

To say that the earth is lovely is because it selflessly dedicates resources to provide guarantee for human survival; to say that the earth is easy to be broken actually means that it is easy to be damaged, such as resource depletion, ecological disasters, etc

The second part of the sixth major question in the synchronous exercise and evaluation of Cowherd and Weaver Girl in the sixth grade of primary school Chinese published by Jiangsu Education Press (the content is below)
2. What does the queen mother look like in a rage? Imagine her actions, language and manner in a few sentences

The queen mother was so angry that she picked up a cup and smashed it on the floor. She said angrily, "this weaver girl is too shameful. She dares to go down to earth without permission. Come on, somebody, go and get the weaver girl back. I'm so angry!"!

Use 0,1,2,3,4 to form a number without repetition
(1) How many natural numbers can be formed
(2) How many three digits can be made up
(3) How many even four digit numbers can be formed
(4) How many even numbers between 3000 and 4000 can be formed

1.
Single digit: 5
Two digit: 4 × 4 = 16
Three digit: 4 × 4 × 3 = 48
Four digits: 4 × 4 × 3 × 2 = 96
Five digits: 4 × 4 × 3 × 2 × 1 = 96
A total of 261 natural numbers can be formed: 5 + 16 + 48 + 96 + 96
two
It can make up three digits: 48
three
1) 0 is in the digit, there are:
1 × 4 × 3 × 2 = 24
2) 0 is not in the individual position, there are:
2 × 3 × 3 × 2 = 36
Four even numbers: 24 + 36 = 60
four
Even numbers between 3000 and 4000 are as follows:
1 × 3 × 3 × 2 = 18

A mathematical problem on the definition of new operation evaluation
Define a new operation: X * y = x + 2Y / X-Y, find the value of (a * b) multiplied by [b * (- a)] when a = (root 3) + 1, B = (root 3) - 1
Make it clear to me,

I'm not sure what x * y = x + 2Y / X-Y means,
If x * y = (x + 2Y) / (X-Y)
Then a * b = (a + 2b) / (a-b) b * (- a) = [B + 2 (- a)] / [b - (- a)] = (b-2a) / (B + a)
A * B times b * (- a) = [2 (b ^ 2-A ^ 2) - 3AB] / (a ^ 2-B ^ 2)
A = (root 3) + 1, B = (root 3) - 1, ab = 2, a ^ 2-B ^ 2 = 4genhao3
Replace it with the original formula = - 2-genhao3 / 2

What is 3.6 minus 3.6 times 0.8
It must be easy to calculate,

Original formula = 3.6 (1-0.8) = 3.6 * 0.2 = 0.72

Given that the solution of the system of equations X-Y = 3 4x + y + k = 0 is also the solution of equation 3x-5y = 5, find the value of K!

x-y=3 ①
4X+Y+K=0②
3x-5y=5③
① * 3 - 3 is y = 2
Take y = 2 into ① to get x = 5
If you take XY into ②, you get k = - 22

Zhang Ying, a saleswoman in a food store, and Li Ni want to pack 1000 plum blossoms separately. Zhang Ying takes 15 plum blossoms for each bag, and Li Ni takes 9 plum blossoms for each bag. As a result, Li Ni packs one less bag than Zhang Ying, and the rest is not enough. How many plum blossoms are left in the end? How many bags did Zhang Ying pack?

1000 △ 15 + 9 = 1000 △ 24 = 41 (bag) 16 (piece) 16-15 = 1 (piece) 41 + 1 = 42 (bag) a: the rest of the plum is one, Zhang Ying has 42 bags

How many solutions of the equation x + 2Y = 8 in the range of positive integers

x=8-2y=2(4-y)
So x is even
2y=8-x
If y is a positive number, then 2Y > 0
8-x>0
x

It's 26 yuan for two snacks and one drink, 18 yuan for one snack and three drinks. How much is it for one snack and one drink
How to make three drinks

26-18 = 8 yuan
One snack is eight yuan more than two drinks
18-8 = 10 yuan
10 / (2 + 3) = 2 (yuan)
(26-2) / 2 = 12 yuan
2 + 12 = 14 (yuan)

3 times 4 times 5 plus 6 times 8 times 10 plus 9 times 12 times 15 plus 12 times 16 times 20 / 1 times 2 times 3 plus 2 times 4 times 6 plus 3 times 6 times 9 plus 4 times 8 times 12

(1*2*3+2*4*6+3*6*9+4*8*12)/(3*4*5+6*8*10+9*12*15+12*16*20)
=(1*2*3)(1+8+27+64)/(3*4*5)(1+8+27+64)
=(1*2*3)/(3*4*5)
=1/10