Solving the problem of mathematical inequality in the first year of junior high school is mainly the

Solution: 1), the unit price is 8 yuan to buy x book, and the unit price is 12 yuan to buy 105-x book.

Column equation: 8x+12(105-x)=1500-4188x+1260-12x=1082

x=A: Because the number cannot be a decimal, Mr. Wang said that he made a mistake.

2), the unit price is 8 yuan to buy x book, the unit price is 12 yuan to buy 105-x book, and the unit price of the notebook is y yuan.

Column equation: 8x+12(105-x)+1*y=1500-4188x+1260-12x+y=1082

4x-y=178

y=4x-178

Only integers that should be less than 10 can be recognized.

4x-178<10---2)

Obtained from (1): x>

From (2): x<47

Integers greater than or less than 47 are only 45 and 46

Take x1 = 45 and x2 = 46 respectively

Substituting x1=45 into y=4x-178 gives :y=2 and x2=46 into y=4x-178 gives y=6

1) If you buy x copies of a book with a unit price of 8 yuan, then buy (105-x) copies of a book with a unit price of 12 yuan.

8x+12(105-x)=1500-4188x+1260-12x=1082

4x=-178

x=Because the number cannot be a decimal, Mr. Wang said that he made a mistake.

2) If you buy x books with a unit price of 8 yuan, then you buy (105-x) books with a unit price of 12 yuan, and the unit price of a notebook is y yuan.

8x+12(105-x)+y=1500-4181260-4x+y=1082

4x-y=178

Because y is less than 10, 4xi is greater than 178 and less than 188x is greater than less than 47

x = 45 or 46

When x=45, y=2

When x=46, y=6

1. If you buy all 8 105 = 840 If you buy all 12 105 = 1260, you will be left with 660 240 respectively

If you buy n books for 12 yuan, you will have 660-4n or 240+4n but 418-240=178 left

178 4=44 remainder 2 so wrong.

2. As analyzed above, the remaining amount before buying a notebook is between 419 427, and after -240 (179 187) can be divisible by 4, and the notebook with 180 is 2 yuan (180-178).

Take 184 to indicate that the notebook is 6 yuan.

One. What is the value of k, and the solution of the equation 3x-3k=5(x+k)+2 for x is positive?

k<-1/4

According to the title: 3x-3k=5x+5k+2

2x=8k+2

x=(8k+2)/(2)

x=-4k-1

x>0，4k-1>0

4k>1

k<-1 4 II. Fill in the blank:

Comparison size: -3

If 2-x 0, x 2;

If. 0, then xy 0;

Algebraic formula. If the value of is not greater than zero, then x

The relationship between A and B is shown in the following figure:

Compare size |a|__b,-

The positive integer solution of inequality 13-3x 0 is

If. x-y|=y-x, is x y;

If x≠ pure peichang y, then x2+|y|__0;

Inequality groups. The solution set is

Three. Multiple choice questions.

1. Among the following formulas, the constant is (a, a

ab、3bb

c、m－5m

d、a2a2

2. The inequality ax about x

The set of solutions for b is , then.

a、a≤0b、a≥0c、a

d, a3, the sum of the integer solutions of the group of inequalities. a、

b, c, d, 4, and if the solution of the equation for x is positive, then the range of m is . a、mb、m

c. Make a chop. n……

Solution: If A is X, then B is 50-X. From the title: 80x+50(50 x)<=3490

x<=33

40x+90(50-x)<=2950

x>=31

So 31<=x<=33

There are three options:

(1) Solution: If you purchase x refrigerators of type B, then 2x*1200+x*1600+(80-2x-x)*2000 132000, 28000 2000x, 14x, then at least 14 refrigerators of type B will be purchased.

2) Solution: If you purchase a refrigerator Y, then purchase 2 refrigerators B, 1200 * y + (y 2) * 1600 + (80-y-y 2) * 2000 132000 (and y 80-y-y 2), 28000 1000y (and y 32), that is, 28 y 32, then type A, that is, y can be.

However, since type A is twice that of type B, the number of units must be an integer, so y should be an even number, then .

So type B, i.e. y 2 can be .

So C species, i.e. (80-y-y2) can be .

There are three options:

A 28, B 14, C 38;

A 30, B 15, C 35;

A 32, B 16, C 32.

(1)3x-y=k+4 (2)

14x=14

x = 1 substituted (2).

3-y=k+4

y=-k-1

x-y=1+k+1=k+2

k|<3

318 7a>28 a>4

The value range of 4a is (4,6).

In the second quadrant, so 1-m<>0, the solution gives 0a, x<=2Since there are five integer solutions, the integer solution should be 2,1,0,-1,-2, so -3<=a<-2

3.Set the discount to the original x%, 1200*x% represents the selling price, and minus the cost price represents the profit.

1200*x%-800>=5%*800

x=7070%=7% off.

4.Solve the equation: x=-1 (4m+5).

Because the solution is a non-positive number, the reed mass is x<=0

1/(4m+5)<=0,4m+5>=0

m>=-5/4

5.Solve equations.

x=-2m 3-1 2Because the solution is a non-positive number, x<=02m 3-1 2<=0

m>=-3/2

6.Solve systems of equations.

The orange sum of the two companions: x=2m

Subtract the two formulas: y=1-m

Because x>y

So 2m>1-m

m>1 3, so the smallest integer is 1

7.Set up x number of Chinese knots.

If purchased, the fee y1 = 10x

If you are hungry for coarseness, the cost is y2 = 4x + 200

10x>=4x+200

x>100/3

When there are more than 33, the production saves.

When less than or equal to 33, purchase savings.

8.If there are x rooms on the first floor, there will be (x+5) on the second floor

4x<48

48>5x

3(x+5)<48

48<4(x+5)

x = 8 or 9 or 10