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If the average of 2, 2, 5 and X is 5, and the average of 3, 4, 5, X and Y is 5, then x=______ ，y=______ ．
The average of ∵ 2,2,5 and X is 5 ∵ 2 + 2 + 5 + x = 4 × 5 ∵ x = 11. The average of ∵ 3,4,5, X and Y is also 5 ∵ 3 + 4 + 5 + 11 + y = 5 × 5 ∵ y = 2, so fill in 11,2
Party A and Party B start from two places AB at the same time and walk towards each other. After 3 hours, they meet at 18 kilometers away from the midpoint. At this time, how far is the distance between Party A and Party B 2:3ab
Let the velocity of a be x and the velocity of B be y;
When a and B meet, the distance they travel is 2:3, and the result is: 3x: 3Y = 2:3; X = (2 / 3) * y;
The total distance is (y + (2 / 3) * y) × 3 = 5Y;
Because the distance that Party A and Party B took when they met was 2:3, the distance that Party A took was less than half of the total distance
(5Y / 2) - (2 / 3) * y × 3 = 18; y = 36;
So the total distance is 5 × 36 = 180
1, - 2,4, - 8,16, - 32
The N-1 power of (- 2)
On a map with a scale of 1:3000000, the distance between a and B is 8.2cm, and their actual distance is () km?
3000000*8.2/1=24600000cm=246km
Find | x + 1 | + 2x + 1 | + The minimum value of ＋| 2011x ＋ 1 |
And this question: | x + 1 | + X + 2 | + + | x + 2011 | minimum
PS: don't copy from the Internet. I've seen it on the Internet. It's wrong!
Let f (x) = | x + 1 | + 2x + 1 | + When x ≥ - 1 / 2011, | x + 1 | + | 2x + 1 | +. + | 2011x + 1 | ≥ | x + 1 + 2x + 1 +. + 2011x + 1 | when (x + 1), (2x + 1), (2011x + 1) are greater than or equal to 0, so when x ≥ - 1 / 2011, the minimum value is f (- 1 / 2011) = 1005
There are several books in class A and class B. It is known that class a accounts for 3 / 7 of the total. If class B gives class a 10 books, the number of books in the two classes is the same
How many books do you have in class A and class B
The total number of solutions is X
3/7x+10=（1-3/7）x-10
1/7x=20
x=140
A: 140 × 3 / 7 = 60 copies
B: 140-60 = 80 copies
Let x > 0, Y > 0, x + y + xy = 2, then the minimum value of X + y is ()
A. 32B. 1+3C. 23-2D. 2-3
Then XY ≤ x + Y2, XY ≤ (x + y) 24, ∵ x + y + xy = 2, ∵ xy = - (x + y) + 2 ≤ (x + y) 24, let t = x + y, then t > 0, substituting the above formula, then T2 + 4t-8 ≥ 0, the solution is t ≤ - 2-23 or t ≥ 23-2, then t ≥ 23-2, so the minimum value of X + y is 23-2, so C is selected
The passenger and freight cars start from a and B at the same time, and run in opposite directions. Five hours later, they meet at the midpoint of the two places, 30km away. Given that the speed ratio of the passenger and freight cars is 5:7, what is the distance between a and B?
30 × 2 ^ (75 + 7-55 + 7) = 60 ^ 212 = 360 km a: the whole journey is 360 km
The basic properties and usage of inequality
What is the use of the basic properties of inequality (for example, if a > b, b > C, then a > C; if a > b, C > D, then a + C > b + D;)? To prove the size of two numbers and to solve the inequality?
If a > 0, b > 0, then a + b > 0; do we use the basic properties of inequality or the theorem that the sum of two positive numbers is positive?
In my opinion, the basic nature of inequality is to solve the problem of the size of two numbers and the solution of inequality, and to find the range of values. I also feel that the use of these theorems is "the sum of positive numbers is a positive number", "the product of two positive numbers is a positive number"... These theorems
..
The properties of inequality are as follows
If the transitivity is a > b, b > C, then a > C
If a > b, C > D, then a + C > b + D (the principle of addition is that the sign direction of inequality is the same, left + left, right + right)
If a > 0, b > 0, then a + b > 0 makes use of the additivity of inequality
Inequality is very useful and has many applications in finding extremum
The passenger and freight cars leave from both places at the same time. The passenger cars travel 66 kilometers every 44 kilometers and the freight cars 44 kilometers every hour. When the freight cars travel 3 / 8 of the whole journey, the passenger cars have exceeded the midpoint of 40 kilometers. How many kilometers are there between the two places?
The distance between a and B is 640 kilometers!
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