First, multiple choice questions

1, multiply x < Y, and get ax>, the condition that A should meet is ().

a . a≥0 b . a≤0 c . a & gt； 0d . a & lt； 0

2, the following inequalities must be correct is ()

A.3x & lt6b .-x & gt； 0c .│x │+ 2 & gt； 0d . x2 & gt； 0

3, the following deformation is incorrect ()

A. 4a+b > obtained from 4a+b & gt；; 4a+5b。 From a>b, get B.

C.by-x & gt； 2y gets x; The solution set of 2 is X.

A.a & gt0b . a & gt； 1 c . a & lt； 0d . a & lt； 1

Second, fill in the blanks

7. If one

8. If two of the three sticks that make up a triangle are 3 cm long, 10 cm, then the length range of the third stick is _ _ _ _ _ _ _, and if the length of the third stick is odd, then the length of the third stick is _ _ _ _ _ _.

9. In the following numbers, -2, -2.5, 0, 1, 6 is the inequality X >；; The solution of 1 has _ _ _ _ _; Yes-x > The solution of 1 has _ _ _ _ _.

10, if the value of the algebraic expression -5 is not greater than the value of -2, the value range of x is _ _ _ _ _ _ _ _.

1 1, the hall is 27.2m long and 14.4m wide, and the ground is filled with square boards with a side length of 1.6m, at least _ _ _ _ _ _ _.

12, Xiaohua's home is 2.4km away from school. One day, Xiaohua left home for school, just halfway there, and found that it was only 12min away from school. If Xiaohua wants to get to school on time, he should walk at an average speed of at least _ _ _ _ _ for the remaining half of the journey.

Third, answer questions.

13, expressed by inequality:

① The difference between 2 times of x and 5 is not greater than1; ② The sum of x and x is non-negative;

③ 30% of the sum of a and 3 is not more than 5; ④ The sum of 20% of A and A is not less than 3 times of A and the difference between 3.

14, solve the following inequality and express its solution set on the number axis.

①3[x-2(x-2)]& gt； 6+3; ②

③ ; ④ .

15, and find the maximum integer value of inequality (2x+1)-(3x+1) >-X. 。

When x is 16, the value of algebraic expression is not less than that of algebraic expression.

17, (Yichang 08) When coal is used for power generation, standard coal refers to coal with a calorific value of 7,000 kcal/kg. In production practice, the coal consumption of required standard coal is generally calculated by converting it into the actual coal consumption with the same heat content. ("kcal/kg" is the unit of calorific value)

Guangming Power Plant needs 0.36kg standard coal for each power generation. The existing coal gangue and Datong coal can be used as production coal. The basic information of these two coals is shown in the table below:

This kind of coal contains heat.

(kcal/kg) Only this kind of coal is used in each round.

Coal consumption of one-degree electricity

(kg/kWh) Average power generation cost per ton of coal burned.

Coal purchase cost

(Yuan/ton) Other expenses

(yuan/ton)

Coal gangue 1000 2.52 150a (a > 0)

Datong coal mine 6000m 600a2

(1) Calculate the coal consumption of each generation of Datong coal in production (that is, the value of m in the table);

(2) According to the requirements of environmental protection, Guangming Power Plant mixes coal gangue with Datong coal to form blended coal with a calorific value of 5000 kcal/kg for power generation. If this blended coal is used, the production cost per power generation 1000 kwh will increase by 5.04 yuan. Look up the value of A in the table. (Production cost = coal purchasing cost+other expenses).

Reference answer:

Analysis of 1. 1, d: x

Therefore, from the inequality property 3, we can know that A.

2. C analysis: 3x

3D resolution:-5x > Divide both sides of -a by -5 to get X, > >. Analysis: A can be determined by the same reason -a, -b and │ A │ B │.

8,7 6+3x, combined 3 [-x+4] > 6+3x, without brackets-3x+12 > 6+3x, shift term, merge-6x >; -6, and the conversion coefficient is x < 1.

② Solution: Denominator 2(2x-5)≤3(3x+ 1)-8, bracket 4x- 10≤9x+3-8, transposed term merged -5x≤5, and conversion coefficient was1x ≥-/kloc-.

③. Solution: Denominators 3 (2-x)-3 (x-5) > 2 (-4x+1)+8 and 6-9x-3x+15 >; -8x+2+8, transfer item merging-4x > -1 1, and the conversion coefficient is1x.

④ Solution: Using the basic properties of fractions, change the decimal denominator into an integer, and remove the brackets 4x-1-10x+7 > 2-4x, transfer item merging-2x > -4, and the conversion coefficient is1x.

Cuddle: Like solving unary linear inequality, solving unary linear equation is based on denominator, brackets, moving terms and merging, and the conversion coefficient is 1. Except for the case where both denominator and conversion coefficient are 1, if both sides of inequality are multiplied (divided) by a negative number, the equal sign should not be changed. In addition, you should not omit the denominator to multiply the item without denominator, and remove the item symbol in brackets.

15,3.

16，x≤3。

17, the solution is obtained from the meaning of the question (1), 0.36×7000=6000m, so m=0.42.

(2) If N kilograms of blended coal is needed for each power generation 1000 kWh, then 0.36×7000× 1000=5000n, and n=504.

If the blended coal contains X kilograms of coal gangue and Y kilograms of Datong coal, then

, solution

According to the meaning, there is

100.8÷ 1000×( 150+a)+403.2÷ 1000×(600+a2)-0.42× 1000÷ 1000×(600+a2)= 5.04

The solution is a 1=0 (irrelevant, omitted), a2=6.

Therefore, the value of a in the table is 6.