Xiao Ding, Xiao Wang three good friends, the age is just three consecutive natural numbers. And their three years multiplied by 504. How old are they?

504=2x2x2x3x3x7=7x8x9,
They are seven, eight and nine

Xiaogang, Xiaohong and Xiaoming do their homework. Xiaogang uses three tenths of an hour more than Xiaohong, and Xiaoming uses one tenth of an hour less than Xiaohong
How long is the difference? If Xiaoming uses one tenth of an hour more than Xiaohong, how long is the difference between Xiaogang and Xiaoming?

3/10+1/10=2/5,
3/10-1/10=1/5.
Need a detailed explanation?

From school to the museum, it took Xiaohong 40 minutes, Xiaoming 0.75 hours and Xiaogang 12 / 7 hours. Which of the three is the fastest?

75 hours = 45 minutes
7 / 12 hours = 35 minutes
So Xiaogang time is the shortest and the fastest

Cars travel 230 kilometers in 6 hours, motorcycles 270 kilometers in 7 hours,

Car speed = 230 km / 6h = 230 / 6 = 28.33
Motorcycle speed = 270 km / 7h = 270 / 7 = 38.5
Motorcycles are fast

① Contains only_ And the maximum number of unknowns is_ The integral equation of is called quadratic equation of one variable, and its general form is_ .
② The common solutions of quadratic equation of one variable are: (1) direct flattening method (2) factorization method (3)_ （4）_ .
③ The root formula of quadratic equation AX & # 178; + BX + C = 0 (a ≠ 0) is_ .
④ The discriminant of the roots of the quadratic equation AX & # 178; + BX + C = 0 (a ≠ 0) is_ .
(1) When_ The equation has two unequal real roots;
(2) When_ The equation has two equal real roots;
(3) When_ The equation has no real roots
⑤ If the two roots of the quadratic equation x & # 178; + PX + q = 0 are x1, X2, then X1 + x2=_ ,x1x2=_ .
⑥ The two solutions of quadratic equation (x-3) (X-5) = 0 are___ .
⑦ The solution equation is: (1) x & # 178; - 2x = 5 (2) (x + 1) (X-2) = x + 1

① Contains only_ 1_ And the maximum number of unknowns is_ 2_ The integral equation of is called quadratic equation of one variable, and its general form is_ ax^2+bx+c=0__ .
② The common solutions of quadratic equation of one variable are: (1) direct flattening method (2) factorization method (3)_ Preparation method (4)_ Formula method
③ The root formula of quadratic equation AX & # 178; + BX + C = 0 (a ≠ 0) is_ x=-b/(2a)±√(b^-4ac)/(2a)__ .
④ The discriminant of the roots of the quadratic equation AX & # 178; + BX + C = 0 (a ≠ 0) is_ △=b^-4ac__ .
(1) When_ △>0__ The equation has two unequal real roots;
(2) When_ △=0__ The equation has two equal real roots;
(3) When_ △

Please sort: solar system, sun, earth, moon, universe, galaxy, total galaxy

Universe Galaxy Galaxy solar system Sun Earth Moon

To solve the equation: 75 plus 10% x minus 15% x equals 74

75 + 10x/100 - 15x/100 =74
15x/100 - 10x/100 =1
15x - 10x =100
x = 20

On liquid pressure
A beaker is full of water. Now a piece of wood is gently put into the beaker, and part of the water overflows. In this process, how does the pressure of water change at the bottom of the beaker
The answer is the same, but according to the
P = pGH, look, the height and density all change, it should be bigger, why
Wood is not equal to the density of water. When part of water becomes wood, the density changes naturally

Put the wood into the water, and the water overflows. Because it was filled with water, the height did not change;
Because it is to find the pressure of water on the bottom of the cup, the density of water should be multiplied by G times the height of water
If you want to know the pressure on the bottom of the cup, you need to multiply the average density of water and wood by G and then by H

After class, Mr. Wang assigned a question: when x = 2013, find the value of (x ^ 2-1) (x + 1) / x ^ 2-x divided by (1 + (x ^ 2 + 1) / 2x)

={(x+1)(x-1))(x+1)/x(x-1)}/(2x/2X+(x+1)^2/2x)
={(x+1)^2(x-1)/x(x-1)}2x/(x+1)^2
=You can write it on the paper

The two trains run in opposite directions. Car a travels 48 kilometers per hour, and car B 60 kilometers per hour. When the two trains go wrong, a passenger on car a starts to count the time when the front of car B passes his window, and it takes 13 seconds for the rear of car B to pass his window?
2. The passenger car and the freight car leave from the two places at the same time. It takes 10 hours for the passenger car to complete the whole journey and 15 hours for the freight car to complete the whole journey. After the two cars meet in the middle of the journey, the passenger car runs another 90 kilometers. At this time, the passenger car type completes 80% of the whole journey, and the distance between the two places is calculated.

Let B car length x / (48 + 60) = 13 / 3600, so x = 0.39km = 390m

Xiao Ding, Xiao Wang three good friends, the age is just three consecutive natural numbers. And their three years multiplied by 504. How old are they?