My brother likes to read extra-curricular books such as journey to the west, China Youth Daily and ancient Chinese invention

My brother likes to read extra-curricular books such as journey to the west, China Youth Daily and ancient Chinese invention

My brother likes to read journey to the west, China Youth Daily, ancient Chinese invention and other extracurricular books

I love reading books about astronomy, especially the children's newspaper

Get rid of it, especially the children's newspaper
The children's newspaper is not a book about astronomy

Given that a, B and C are positive numbers, it is proved that 2 (A3 + B3 + C3) ≥ A2 (B + C) + B2 (a + C) + C2 (a + b) by using ordering inequality

Prove: first prove: A3 + B3 ≥ A2B + AB2, ∵ (A3 + B3) - (A2B + AB2) = A2 (a-b) - B2 (a-b) = (A2-B2) (a-b) = (a + b) (a-b) 2 ≥ 0, ∵ A3 + B3 ≥ A2B + AB2, take the condition of equal sign is a = B, similarly, add three formulas of A3 + B3 ≥ A2B + AB2, A3 + C3 ≥ A2C + ac2, B3 + C3 ≥ B2C + BC2, get: 2 (A3 + B3 + C3) ≥ A2 (B + C) + B2 (a + B), take the condition of equal sign is a =b=c，∴2（a3+b3+c3）≥a2（b+c）+b2（a+c）+c2（a+b）．

One fifth of the number a is equal to one seventh of the number B. how many percent more is the number B than the number a?
Be sure to be 100% correct

One fifth of a is equal to one seventh of B
B is a: 1 / 5 △ 1 / 7 = 7 / 5
Number B is more than number A: 7 / 5-1 = 2 / 5 = 40%

The use of mean inequality
I have a question
I hope you can help solve it
We have just entered high school and started to contact the mean inequality
Is it any fixed value of 2 numbers, and these two numbers are greater than 0
Can we use the mean inequality to find the maximum or minimum of one of the numbers?
For example, we have a circuit problem. R1 + R2 = 12
Then the maximum value of R1 (12-r1) is required. The calculated R1 is 6
But in R1 + R2 = 12, the minimum R1 can be 0.1 a
Is my statement wrong?
It seems wrong
So the mean value inequality
1. Conditions of use
2. Scope of application
3. There are always misunderstandings
What is it
I hope you can give me the answer. But please don't make it too complicated
thank you.

Child, the circuit has nothing to do with the mean value. It turns that into - R1 + 12r1. When the knowledge of junior high school R1 is - B / 2a, that is, when it is 6, this formula reaches the maximum. You can't help but understand this. Then 6 is just less than 12, that is, it is within its value range (0,12), so it is it
Mean ah, this is more complicated... To analyze specific problems

A and B start from a and B at the same time, and run in opposite directions. After 1.5 hours, they meet at 18 kilometers from the midpoint. It is known that the speed of a is 2, 2 times that of B
How many kilometers did the two cars travel when they met

Suppose: the speed of car B is x km / h,
2*1.5X-1.5X=18*2
X=24
2X = 48 km / h
24 * 1.5 = 36 km
48 * 1.5 = 72km
Car a has traveled 72 kilometers each
Car B has traveled 36 kilometers each

The mathematical problem of inequality,
1. When k takes what value, the solution of the system of equations {3x-y = 2,5x + 2Y = 2K satisfies x + y

3X-Y=2 (1)
5X+2Y=2K (2)
(2)*4-(1)*3
20X+8Y-9X+3Y=8K-6
11X+11Y=8K-6
X+Y

The distance between a and B is 360 km. The passenger cars travel 40 km per hour and the freight cars 60 km per hour. At 8 a.m., the two cars drive from a to B at the same time
When will the two vehicles meet each other?

15:30

It is known that the side length of the square ABCD is 13, the distance from a point p outside the plane ABCD to each vertex of the square is 13, m and N are the points on PA and BD respectively, and PM: Ma = BN: nd = 5:8, as shown in the figure. (1) prove: the line Mn ‖ plane PBC; (2) find the length of the line Mn

(1) It is proved that by connecting an and extending the intersection with BC at point E, from PM: Ma = BN: nd = 5:8, en: Na = BN: nd = MP: Ma = 5:8 can be obtained (2) because △ PBC is an equilateral triangle with 13 sides, the cosine theorem obtains that Pe2 = Pb2 + be2-2pb · ebcos60 ° = 132 + (132) 2-2 × 13 × 132 × 12 = 828164, ‖ PE = 918

Team a and team B built a road together. When they finished the task, team a built 815% of the road. If team B finished it alone in 24 days, how many days did team a finish it alone? (Qingshan District, Wuhan City)

The working time of team a and team B: (1-815) △ 124, = 715 × 24, = 565 (days); team a does it alone for several days: 1 △ 815 △ 565, = 1 △ 121, = 21 (days). Answer: team a does it alone for 21 days