Math Problems Inequalities Questions Thank you for giving you 30 points

After reading that the questions are quite complicated, I decided to help you.

1. Because A's salary is higher than B's, the less A has, the less the total monthly salary. There is a reason: "A" = 2 * B, so let A = 2 * B. Then it is solved by A + B = 150: A recruits 100 people, and B recruits 50 people.

2. List the odd numbers within 21 first: 1,3,5,7,11,13,17,19, then it is easy to meet the conditions

3,5,7；3,5,11；A total of 10 groups. Arrange from small to large like me and you won't leak it.

3，（1）y1= ，y2=

2) If the use time is short, it is cost-effective to buy incandescent lamps; If you use it for a long time, it is cost-effective to buy energy-saving lamps.

3) x=6000, bring in the seeking: y1=, y2= obviously save money with energy-saving lamps, and the money saved is: y1-y2=yuan.

It's best to do the calculations yourself in case I don't get it right, and it can also deepen your understanding of the problem.

1. Let A: x person, then B: (150-x) person, x 2 (150-x), and get x 100

Salary: y = 1000x + 600 (150-x) = 90000 + 400x

So the smaller the x, the smaller the y, thus: A: 100 people, B: 50 people.

Solution: At least x copies of the questionnaire should be printed.

3x>150

A: Then print at least 150 questionnaires.

2190x<=2190*(1+10%) x<=2409-803=At least discounted.

60x-20*60*>=0 x>16 When there are more than 16 people, it is cheaper to set x A saplings 60x+90 (400-x)=29400 x = 220 A saplings 220 B 180

Let B x60*2x+90x<=14700 x<=70 up to 70

1, set x discount, 2190x+365*<=2190*, x<=2, (1), province (18-20 * yuan, (2), when x<20, 60*<60*x, get 163, (1) A x, B y, get x + y = 400, 60x + 90y = 29400, get the meridian = 220, y = 180.

2) A x, B 1 2x, 60x+90*2x<=14700, get x<=140, so A is up to 140

Discounts are cheaper when the discount is greater than 16 people.

3. Set x A sapling 60x+90 (400-x) = 29400 x = 220, A sapling 220 B 180

Set B x up to 70

Answer: When the bottom surface is a square with a side length of 40 meters, the total cost of the pool is the lowest, which is 297,600 yuan.

Solution: Let the length and width of the bottom surface be x, y (or set to width and length, it doesn't matter), the minimum total cost is m

According to the meaning of the title, x·y·3=4800, so xy=1600

The value of m should be equal to the cost of the bottom surface + the cost of the four-sided pool wall, so.

m=150xy+120[2(x·3)+2(y·3)]

150×1600+720（x+y）

720 (x+y) + 240000 (according to x2+y2 2xy, there is :)

720×2√(xy)+240000=720×80+240000=297600;

Therefore, M 297600, that is, the minimum cost is 297600 yuan.

To have the lowest cost, i.e. to meet x+y=2 (xy), so x=y, i.e. x=y=40 meters.

b.(n-3)/2=-1 n=1

c.(22-3*2) 3=5 remainder 1

m, to have 4 integer solutions, it must contain 6, not 7

Because: 2x-a -3

So: x (-3+a) 2

And because: x -1

So: (-3+a) 2=-1

So: a=1, choose b

7c 8 a.I don't know if it's right or not. Move both questions to a bit.