The purchase price and selling price of the refrigerator and color TV of the designated model of "home appliances to the countryside" in Green Valley Shopping Mall are shown in the table below: the purchase price of the refrigerator and color TV of the category (yuan / set) is 23201900, and the selling price (yuan / set) is 24201980 (1) according to the national policy, farmers can enjoy the government subsidy of 13% of the selling price when they buy "home appliances to the countryside" Government subsidies? (2) In order to meet the needs of farmers, the shopping mall decided to purchase 40 refrigerators and color TV sets with no more than 85000 yuan, and the number of refrigerators is no less than 56% of the number of color TV sets. ① please help the shopping mall design the corresponding purchase plan; ② which purchase plan will the shopping mall get the most profit (profit = selling price purchase price), and what is the maximum profit?

The purchase price and selling price of the refrigerator and color TV of the designated model of "home appliances to the countryside" in Green Valley Shopping Mall are shown in the table below: the purchase price of the refrigerator and color TV of the category (yuan / set) is 23201900, and the selling price (yuan / set) is 24201980 (1) according to the national policy, farmers can enjoy the government subsidy of 13% of the selling price when they buy "home appliances to the countryside" Government subsidies? (2) In order to meet the needs of farmers, the shopping mall decided to purchase 40 refrigerators and color TV sets with no more than 85000 yuan, and the number of refrigerators is no less than 56% of the number of color TV sets. ① please help the shopping mall design the corresponding purchase plan; ② which purchase plan will the shopping mall get the most profit (profit = selling price purchase price), and what is the maximum profit?

(1) (2420 + 1980) × 13% = 572, a: you can enjoy the subsidy of 572 yuan from the government; (2) if you purchase x refrigerators, you purchase (40-x) color TV sets, according to the title, 2320x + 1900 (40-x) ≤ 85000; ① , X ≥ 56 (40-x) 2, 18211 ≤ x ≤ 2137, and ∵ x is a positive integer.. x = 19, 20, 21. There are three purchase schemes in the shopping mall. Scheme 1: 19 refrigerators and 21 color TV sets. Scheme 2: 20 refrigerators and 20 color TV sets. Scheme 3: 21 refrigerators and 19 color TV sets. ② the total profit of the shopping mall is y yuan= (2420-2320) x + (1980-1900) (40-x) = 20x + 3200, ∵ 20 > 0, ∵ y increases with the increase of X, ∵ when x = 21, y max = 20 × 21 + 3200 = 3620 yuan

1. If a is a rational number, the following formula must be greater than 0 (&# 160; &# 160; &# 160;)
A. The square of the root sign a &# 160; B, | a + 1 | &# 160; the third power of C and a &# 160; the square of D and a plus 1
2. If n is an integer, even numbers can be expressed as________ The odd number can be expressed as________ Three consecutive even numbers can be expressed as__________ .
If x + y = 1, then 3-2x-2y=________

1,D
Analysis: when a, a = 0, the square of root a is 0, so it is wrong
B. When a = - 1 | a + 1 | = 0, it is wrong
C. When a is negative, the third power of a is negative
If n is an integer, even numbers can be expressed as____ 2n____ The odd number can be expressed as___ 2n+1_____ Three consecutive even numbers can be expressed as____ 2n 2n+2 2n+4______ .
X + y = 1, then 3-2x-2y=___ 1_____ Analysis of 3-2x-2y = 3-2 * (x + y) = 3-2 * 1 = 1

Xiao Ming took a bus with his parents to the scenic spot 200 kilometers away from home on October 2. They set out from home at 8:00 a.m. at 10:00 a.m., Xiao Ming found that if the average speed in the future is the same as that in the past, it will take another hour to reach the destination. Q: how much distance did their car travel at 10:00 a.m

100 / 4 = 25 km
25 * 3 = 75 km

How about going to the library

How about going to the library~

The absolute value of the number represented by the point on the number axis whose distance from the origin is 4 units of length is__ The number represented is__ They are mutual__ .
The absolute value of the number represented by the point with 4 unit length on the number axis and the origin is__ The number represented by is__ They are mutual__

The absolute value of the number represented by the point whose distance from the origin is 4 unit length on the number axis is 4, and the number represented is ± 4, which are opposite to each other

The function f (x) = x & # 178; + 2 (A-1) x + 21 is known. If f (x) is a decreasing function on (- ∞, 4), the value range of a is obtained
The known function f (x) = x & # 178; + 2 (A-1) x + 2
1. If f (x) is a decreasing function on (- ∞, 4), the value range of a is obtained
2. If x ∈ [- 5,5], find the maximum and minimum of F (x)
The first question is just the answer
Second, ask the great God for detailed explanation

(1) A is less than or equal to - 3
(2) Functions on 1-A symmetry
When a = 0, the maximum value of the function is 27 when x = 5 or - 5, and the minimum value is 2 when x = 0
When a is greater than 1 and less than 6, 1-A is less than 0 and greater than - 5, and the axis of symmetry is between 0 and - 5. Therefore, when x = 5, the maximum value of the function is 17 + 10a, and when x = 1-A, the minimum value is - A square + 2A + 1
When a is greater than or equal to 6, 1-A is greater than or equal to - 5, and the axis of symmetry is between negative infinity and - 5. Therefore, when x = 5, the maximum value of the function is 17 + 10a, and when x = - 5, the minimum value is 37-10a
When a is less than 1 and greater than - 4, 1-A is less than 5 and greater than 0, and the axis of symmetry is between 0 and 5. Therefore, when x = - 5, the maximum value of the function is 37-10a, and when x = 1-A, the minimum value is - a square + 2A + 1
When a is less than or equal to - 4, 1-A is less than or equal to 5, and the axis of symmetry is between 0 and positive infinity. Therefore, when x = - 5, the maximum value of the function is 37-10a, and when x = 5, the minimum value is 17 + 10A

With a happy mood and brisk pace, I boarded the Dai bamboo house

With a happy mood, I stepped up the Dai bamboo house with a brisk pace
The pace can't be pregnant

（m+n）2+6（m2-n2）+9（m-n）2．

The original formula = (M + n) 2 + 6 (m-n) (M + n) + 9 (m-n) 2, = [(M + n) + 3 (m-n)] 2, = (4m-2n) 2, = 4 (2m-n) 2

What is the inverse of the function y = 2x + 1? Why?

y=x-1/2
Just solve the above equation, express x with y, and exchange X and y

Mother wants to test Xiaogang who is in the seventh grade. Mother wants to test her son Xiaogang who is in the seventh grade. She asks her son to divide the rectangle with an area of 1 into two rectangles with an area of 1 / 2, then divide the rectangle with an area of 1 / 2 into two rectangles with an area of 1 / 4, and then divide the rectangle with an area of 1 / 4 into two rectangles with an area of 1 / 8
1. Seek the law
2. Calculation by law: 1 / 2 + 1 / 4 + 1 / 8 + 1 / 16 + 1 / 32 + 1 / 64 + 1 / 128 + 1 / 256
3. Calculation: 1 / 2 + 1 / 4 + 1 / 8 + 1 / 16 + 1 / 32 + 1 / 64 + 1 / 128 + 1 / 256 + 1 / 512 + 1 / 1024

It's too late. If you see it, you can answer it. In fact, if you input 1 / 2 + 1 / 4 + 1 / 8 + 1 / 16 into Baidu, you can find the answer. In fact, there is a ready-made formula. You can imagine that when you add 1 / 2 + 1 / 4, there are still 1 / 4 squares that are not included in the calculation, and when you add 1 / 2 + 1 / 4 + 1 / 8 + 1 / 16, there are still 1 / 16 squares that are not included in the calculation