These math problems. In the second year of junior high school, what about the inequality, the master

1. I don't know.

2,, established established not established.

3.I don't know, greater than less than less than (your question conditions don't seem to be complete) < x is the number of students).

5.x>4 x minus 3/2 x<-3 x>3 x>minus 5/6 x 6

6.Right, no.

Answer: A flower condition: 80a + 50b 3490 B flower condition: 40a + 90b 2950

a+b=50

80A+50(50-A) 3490 A 3380(50-B)+50B 3490 B 1740A+90(50-A) 2950 A 3140(50-B)+90B 2950 B 19 Therefore, there are only three matching schemes:

a=33，b=17

a=32，b=18

a=31，b=19

a=33,b=17 cost: 33*800+17*960=42720a=32,b=18 cost: 32*800+18*960=42880a=31,b=19 cost: 31*800+19*960=43040, so a=33,b=17 has the lowest cost, and the cost is 42,720 yuan.

Solution: 1. If you order X sets of A, then B is 30-x sets.

The equation is obtained according to the meaning of the question.

7600≦350x+200(30-x)≦80007600≦150x+6000≦8000

1600≦150x≦2000

So there are three schemes: 1. 11 sets of A and 19 sets of B.

2. 12 sets of A and 18 sets of B.

3. 13 sets of A and 17 sets of B.

2. Scheme 1: (400-350) 11 + (300-200) 19 = 2450

Scheme 2: (400-350) 12 + (300-200) 18 = 2400 Scheme 3: (400-350) 13 + (300-200) 17 = 2350 Scheme 1 is the most profitable.

If you buy X pieces of type A, then 30-x pieces of type B, then there are:

7600≤350x+200(30-x)≤8000;

7600≤150x+6000≤8000;

1600≤150x≤2000;

160/15≤x≤40/3;

The schemes are: a: A11, B19;

b: A12, B18;

C: A13, B17;

2) A: profit = 11 * 50 + 19 * 100 = 2450 yuan;

b: profit = 12 * 50 + 18 * 100 = 2400 yuan;

c: profit = 13 * 50 + 17 * 100 = 2350 yuan;

So option A is the most profitable.

Set up x pieces of clothing A and Y pieces of clothing B. According to the title.

7600≤350x+200y≤8000

x+y=30

From these two equations, x can be 11, 12, 13

In the second question, you can compare the results obtained by substituting the value of x into 400x+300y, and you can know which profit is bigger.

There are x dormitories, and there are 4x+19 students.

6(x-1)<4x+19 <6x

19/2 < x < 25/2

x=10 11 12

In this way, there are x dormitories, and there are Y students, so you can get it from the question: 4x+19=y,6(x-1)6(x-1)<4x+19<6x, you have to understand it

Solution: Let the children have Y people and the pencils have x people.

x＝5y＋2 ①0＜x－6﹙y－1﹚＜2 ②

Substitute : 0 5 y 2 6 y 1 2 3 y 1

1 y 3y is the number of children.

y is a non-negative integer.

y＝2x＝5y＋2＝12

A: The number of children is 2 and there are 12 pencils.

Suppose the number of children is x and the number of pencils is y

There is 5x+2=y

6x-2=y

The solution is x=4, y=22

There are x number of students. The equation for the number of pencils in the column is 5x+2=6(x-1)+1 or 5x+2=6(x-1).

The solution is x=7 or x=8

The corresponding pencil number is 37 or 42

The child is set to x and the number of pencils is set to y

then y=5x+2

y=6x-2

So x=4 y=22

Untie; The line y1=kx+b and y2=-x-1 intersect the point p, and the abscissa of p point is -2, so the ordinate is 1, i.e., p (-2,1).

Because the straight line y1=kx+b passes through the point p (-2,1) a(-3,0).

So -2k+b=1 -3k+b=0 k=1 b=3 y1=x+3

When y1y2<0 y1 0 y2 0 or y1 0 y2 0

i.e. x+30 or x+3 0

x-1 0 solution gives x -1 -x-1 0 solution x -3

The value of x can be x>-1 or x<-3

You can also look directly at the image to find the common part.

Choke, the answer is that you are right just miscalculated sorry.

2.（10-2-2）x≥600-120

6x≥480

4.Because after the conversion, the greater than sign is changed to the less than sign, so m-2 0m 25-x+1＞-y+1

x y so 5x-4 5y-4

The first question is not a question about writing conditions.

3：x<0 ；

4：m<2 ；

5：5x-4<5y-4 ；

I would like to explain here, I am sorry that I don't understand the meaning of question 1.

Question 2 analysis: the original task was to dig 600 in 10 days, and now it takes two days to dig 120, that is, it still needs (10-2) days to dig (600-120), and now the plan has changed: dig the rest two days in advance, then it is [(10-2)-2] day digging (600-120).

1;Empty.

2: Let the minimum digging xm per day be, then the resulting inequality is: (10-2-2) x (600-120).

3：x<0

4：m<2

5:5x-4<5y-4