All natural numbers are integers, and all integers are natural numbers______ (judge right or wrong)

All natural numbers are integers, and all integers are natural numbers______ (judge right or wrong)

From the analysis, we can see that natural numbers are integers and integers are natural numbers

Must integers be natural numbers

Natural numbers are positive integers, but integers include positive and negative integers,
Therefore, integers are not necessarily natural numbers

Solve the equation, if you calculate, 1 / 1-9x ^ 2-3x + 1 / 3x-1 = 1-3x / 1 + 3x
It's like this: 1 / (1-9x ^ 2) - (3x + 1) / (3x-1) = (1-3x) / (1 + 3x)

Is your 1 / 3x, X in the numerator or denominator? Is it in the form of 1 / (3x)?

The bookshelf is full of books

Dusty. Messy

The premise is 2 = 1 * 2; 2 + 4 = 2 * 3; 2 + 4 + 6 = 3 * 4
According to the law of the above formula, 2002 + 2004 + 2006 + 2008 + +2050=?
Note: do not use a + B + C + +Z = [(a + Z) * number of terms] / 2

=2000*25+(2+4+.+50)
=50000+25*26
=55150

Simple calculation 6.8 * 3.4 + 15.9 * 3.2

6.8*3.4+15.9*3.2
=(10-3.2)*3.4+15.9*3.2
=10*3.4+(15.9-3.4)*3.2
=34+12.5*3.2
=74

Xiaoming is one twelfth higher than Xiaojun. Xiaojun is 12 cm shorter than Xiaoming. How many meters is Xiaoming?

Xiaoming 156, Xiaojun 144

1+1,2+3,3+5,4+7,1+9,2+11,3+13,4+15,1+17,2+19,… So according to this rule, how many results is 2013?
The correct answer is 1006, but what is the process? Please write about the process

The first number of the formula is 1,2,3,4, cyclic, and the second number is odd
The first and third results of cyclic numbers are even, the second and fourth results are odd, and 2013 is odd
2013-2=2011
（2011+1）/2=1006
Checking calculation: 2 + 1006 * 2-1 = 2013
According to this rule, the 1006th result is 2013

A skier with a weight of 60 kg stands on a skis. Each skis is 2 meters long, 0.1 meters wide and weighs 10 Niu. The pressure on the horizontal snow surface is calculated when the skier stands. (G is taken as 10 Niu / kg)
A student's solution is as follows:
The stress area of horizontal snow surface when athletes stand: S = AB = 2m × 0.1M = 0.2m2
G = mg = 60 kg × 10 N / kg = 600 n
When the athlete stands on the horizontal snow surface, the pressure on the horizontal snow surface is f = G
According to the pressure formula P = f / S = 600 n / 0.2 M2 = 3000 pa
A
Please check the student's problem solving process and results, point out the mistakes and correct them
Don't copy, just the original

The stress area of horizontal snow surface when athletes stand: 2S = 2Ab = 2 × 2m × 0.1M = 0.4m2
G = mg = 60 kg × 10 N / kg = 600 n
When the athlete stands on the horizontal snow surface, the pressure on the horizontal snow surface is f = g 1 + G 2 = 620 n
According to the pressure formula P = f / 2S = 620 n / 0.4 M2 = 1550 pa

There is 270 ml of water in a cuboid container, and a cube iron block with 3 cm edge length is completely put into the water. The water depth is 6.6 meters, which is more than 10% of the original water depth
Rice?

It's 6.6cm, right
The volume of iron is 3 × 3 × 3 = 27 cubic centimeter
So now the total volume is 270 + 27 = 297 cubic centimeters
So the bottom area of the container is 297 △ 6.6 = 45 square centimeters
So the original water depth is 270 △ 45 = 6cm