First, multiple-choice questions:
The solution set of 1. inequality is ()
A.B. C. D。
2. The following inequality must be established ()
A.5a & gt4a B.x+2-2a D
3. Inequality-3x+6 >; The positive integer solution of 0 has ()
A. 1 B.2 C.3 D
4. The solution set of inequality ≥-2 is expressed on the number axis, and the correct one is ().
A B C D
5. As shown on the right, the range of independent variables at that time was ()
A.b.c.d title (5)
6. In order to make the algebraic expression meaningful, the value range of is ()
A.B. C. D。
7. The inequality listed in "The difference between 2 times of x and 3 is not more than 8" is ().
A.2x-3≤8 B.2x-3≥8 C.2x-38
Second, fill in the blanks:
8. When, the value of algebraic expression is positive.
9. The integer solution of inequality is:
10. Expressed by inequality: the difference between twice m and n is not negative.
1 1.if-3a >； -3b, and then (fill in inequality number).
Third, answer questions:
12. Solving inequality, which represents the solution set on the number axis;
( 1)5x-6≤2(x+3) (2)
13. Solving inequalities:
( 1) (2)
14. As shown in the figure, according to the information in the figure.
(1). Find the values of m and n;
(2) when x is what value, y1>; y2？
15. Every March 12 Arbor Day, several people from a tree planting group in a school plant trees together and plant several trees. If everyone plants 4 trees, the remaining 20 trees will not be planted. If each person plants 8 trees, one person will plant fewer trees than others (but there are trees). How many people are there in this tree planting group? * * * How many trees are there?
16. In the standardization construction project of primary and secondary schools in Dongying, a school plans to purchase a batch of computers and electronic whiteboards. According to market research, it costs 35,000 yuan to buy 1 computer and two electronic whiteboards, and 25,000 yuan to buy two computers and 1 electronic whiteboards.
(1) How much is each electronic whiteboard per computer?
(2) According to the actual situation of the school, it is necessary to buy 30 computers and electronic whiteboards, with a total cost of not more than 300,000 yuan, but not less than 280,000 yuan. Please find out several purchasing schemes through calculation, which scheme has the lowest cost.