Author: admin Question Source: Original hits on this site: 526 Update time: April 22, 2009
1. Multiple choice questions (3 points for each question, 30 points for * * *)
The degree of 1. polynomial 3x2y+2y- 1 is ().
A, 1 time b, 2 times c, 3 times d, 4 times
2. The volume of a square with side length a is a3. If the side length is doubled, the volume is ().
a、2a3 B、8a3 C、 16 a3 D、a3
3. According to the data of the fifth national census in 2000, the total population of China is1295,330,000, with an accuracy of ().
a、 1.30× 109 B、 1.259× 109 C、 1.29× 109 D、 1.3× 109
4. The following four groups of numbers are the lengths of three sticks, and the one that can't be spelled into a triangle with them is ().
a、3cm、4cm、5cm B、 12cm、 12cm、 1cmC、 13cm、 12cm、20cm D、8cm、7cm、 16cm
5. It is known that the degrees of the three internal angles of △ABC are A, 2a and 3a respectively. This triangle is () triangle.
A, acute triangle B, right triangle C, obtuse triangle D, uncertainty
6. The national flag is the symbol of a country, and the national flags of the following four countries are not axisymmetric ()
A, Vietnam b, Australia
C, Canada d, Cambodia
7. Which of the following pictures can roughly reflect the speed change of sprinters from the starting point to the end point in the competition ()
A, B, C, D,
8. As shown in the figure, △ Abd△ CBE is known, and the following conclusion is incorrect ().
a、∠CBE=∠ABD B、BE=BD C、∠CEB=∠BDE D、AE=ED
9. Fold a rectangular piece of paper in half, then fold it in half and tear off a corner of the rectangle. The opened graph must have a () axis of symmetry.
A, a b, two c, three d and four.
10. There are two kinds of floors in the room, of which the area of the black floor is half that of the white floor, and there is a treasure hidden under the floor. The probability of hiding under the white floor is ()
a、 1 B、C、D、
I will fill it out. (3 points for each small question, *** 15 points)
1 1.22+22+22+22=____________。
12. When two sides of a triangle are 5cm and 8cm respectively, the range of the length of the third side is _ _ _ _ _.
13. The height of a triangle is x, the length of its base is 3, and the relationship between the triangle area s and the height x is _ _ _ _ _ _ _ _ _ _.
14. As shown in the figure, O is the midpoint between AB and CD, so the reason for △ OAC △ OBD is _ _ _ _ _ _ _.
15. There are two red balls, three white balls and five black balls in the schoolbag. Choose a ball from them, and the probability of touching the red ball is _ _ _ _ _.
Three. Problem solving (6 points for each small question, ***24 points)
16.(2mn+ 1)(2mn- 1)-(2m2n 2+2)
17. There is a question "Calculate the value of (2x3-3x2y-2xy2)-(x3-2xy2+y2)+(-x3-3x2y-y2), where x =, y =- 1." A classmate mistakenly copied X = as X =-, but his calculation result is also correct. What do you think is going on?
18. As shown in the figure, AB∥CD and straight line EF intersect AB and CD at points E and F, respectively, and EG bisects ∠BEF and intersects CD at point G, ∠ EFG = 500, so as to find the degree of ∠BEG.
19. Kobayashi accidentally broke a triangular glass (as shown in the figure) on the door of the decorative cabinet while helping grandma clean. Kobayashi decided to use his pocket money to buy a glass of the same size in a glass shop for his father to install.
(1) Please use a ruler to help Xiao Lin draw a figure identical to the original triangle in the box below. (Don't write, leave traces of painting)
(2) Kobayashi found a glass shop with drawings, and the salesperson measured it. The three sides of the triangle were 20cm, 15cm and 25cm respectively. The salesman said that the glass was sold by the square. Please help Xiao Lin estimate how many square meters it takes to buy a piece of glass of the same size.
4. Answer the questions. (7 points for each small question, ***2 1 point)
20. The picture below shows several 4×4 squares. Please draw four different divisions along the grid line and divide it into two congruent figures.
2 1. As shown in the figure, AB∨CD, AE = CF, ED∨BF, what do you think of △ ABF △ CDE in the figure? Please provide a justification for the answer.
22. Note that this short question provides two optional questions. Please answer any of the following 22- 1 and 22-2 questions, and do one more question without scoring.
22- 1. This painting is part of the butterfly pattern. Please draw another part of the pattern to make it take L as the symmetry axis. At this time, you will get a complete pattern of a beautiful butterfly. Give it a try. (non-writing method)
22-2. The picture below shows the time displayed by the electronic clock in the mirror. When do you think the actual time should be? Draw it in the back.
5. Answer the questions. (Each small question 10, ***30)
23. The following table is a statistical table of population density in China (population density is the population per square kilometer). Please draw a statistical map, as vivid as possible. And tell me what information you can get from the picture.
Year194919591969197919891999 2003.
Population density is 57 7084102118131134.
24. Analyze the relationship between variables reflected in the figure below, imagine an actual situation suitable for it, and write it out for everyone to share.
25. Choose one of the following two questions to answer.
25- 1. Xiao Ke plays games with Xiao Ai. Xiaoke has a group of cartoons, one is Mickey Mouse, and the other two are Snoopy. Let Xiao Ai draw two pictures from among them. If Mickey Mouse and Snoopy are taken away, Xiao Ai loses and Xiao Ke wins. Is the game fair? What are the chances of Xiao Ai winning?
25-2. Both China Sports Lottery and China Welfare Lottery have 3D gameplay, and the gameplay is a note by 2 yuan. If the selected three digits are the same as those drawn in the lucky draw, you will get a bonus of 1 1,000 yuan. Would you please explain the winning probability of this game with your knowledge? How many bets do I have to buy to win the prize? How to buy?
Reference answer: (There is no unique answer to the question about drawing in this answer, and this answer is for reference only)
1. Multiple choice question: CBADB BADBD
2. I will fill in:11.1612. More than 3 and less than 13 13. S = x 14。 A triangle with two equal angles is congruent.
3. Fill in the blanks:16.2mn2317. The original formula is simplified to -6x2y-2y2, and x2 is the same whether X is or-. 18.650
19.0.05438+05m2
IV.20. (The answer is not unique)
2 1.ED∨BF gets ∠ AFB = ∠ CED, AB∨CD gets ∠ A = ∠ C; Ae = cf plus EF on both sides can get af = ce. According to the corner theorem, two triangles can be congruent.
22.
( 1) (2)
V.23 (The answer is not unique)
As can be seen from the picture, the population of our country is increasing. Since 1999, population growth has been slow under the control of the state. (as long as it makes sense)
24. (The answer is not unique) Xiaoming went to school. After walking for a while, he saw an acquaintance and chatted with him for a while. He found that he was going to be late. After saying goodbye to his acquaintances, he hurried to school.
25.( 1) The game is unfair, and the probability that Xiao Ai will win is.
(2) The probability of winning the 2)3D grand prize is that if you want to win the grand prize, you must buy at least 1000, from 00 1 to 999.
1. Multiple choice questions (3 points for each question, 30 points for * * *)
The degree of 1. polynomial 3x2y+2y- 1 is ().
A, 1 time b, 2 times c, 3 times d, 4 times
2. The volume of a square with side length a is a3. If the side length is doubled, the volume is ().
a、2a3 B、8a3 C、 16 a3 D、a3
3. According to the data of the fifth national census in 2000, the total population of China is1295,330,000, with an accuracy of ().
a、 1.30× 109 B、 1.259× 109 C、 1.29× 109 D、 1.3× 109
4. The following four groups of numbers are the lengths of three sticks, and the one that can't be spelled into a triangle with them is ().
a、3cm、4cm、5cm B、 12cm、 12cm、 1cmC、 13cm、 12cm、20cm D、8cm、7cm、 16cm
5. It is known that the degrees of the three internal angles of △ABC are A, 2a and 3a respectively. This triangle is () triangle.
A, acute triangle B, right triangle C, obtuse triangle D, uncertainty
6. The national flag is the symbol of a country, and the national flags of the following four countries are not axisymmetric ()
A, Vietnam b, Australia
C, Canada d, Cambodia
7. Which of the following pictures can roughly reflect the speed change of sprinters from the starting point to the end point in the competition ()
A, B, C, D,
9. Fold a rectangular piece of paper in half, then fold it in half and tear off a corner of the rectangle. The opened graph must have a () axis of symmetry.
A, a b, two c, three d and four.
10. There are two kinds of floors in the room, of which the area of the black floor is half that of the white floor, and there is a treasure hidden under the floor. The probability of hiding under the white floor is ()
a、 1 B、C、D、
I will fill it out. (3 points for each small question, *** 15 points)
1 1.22+22+22+22=____________。
12. When two sides of a triangle are 5cm and 8cm respectively, the range of the length of the third side is _ _ _ _ _.
13. The height of a triangle is x, the length of its base is 3, and the relationship between the triangle area s and the height x is _ _ _ _ _ _ _ _ _.
There are two red balls, three white balls and five black balls in the bag, and the probability of touching the red ball is _ _ _ _ _.
Three. Problem solving (6 points for each small question, ***24 points)
16.(2mn+ 1)(2mn- 1)-(2m2n 2+2)
17. There is a question "Calculate the value of (2x3-3x2y-2xy2)-(x3-2xy2+y2)+(-x3-3x2y-y2), where x =, y =- 1." A classmate mistakenly copied X = as X =-, but his calculation result is also correct. What do you think is going on? 19. Kobayashi accidentally broke a triangular glass (as shown in the figure) on the door of the decorative cabinet while helping grandma clean. Kobayashi decided to use his pocket money to buy a glass of the same size in a glass shop for his father to install.
(1) Please use a ruler to help Xiao Lin draw a figure identical to the original triangle in the box below. (Don't write, leave traces of painting)
(2) Kobayashi found the glass shop with the drawings. The salesgirl measured it, and the three sides of the triangle were 20cm,15cm and 25cm respectively. The salesman said that the glass was sold by the square. Please help Xiao Lin estimate how many square meters it takes to buy a piece of glass of the same size.
4. Answer the questions. (7 points for each small question, ***2 1 point)
20. The picture below shows several 4×4 squares. Please draw four different divisions along the grid line and divide it into two congruent figures.
22. Note that this short question provides two optional questions. Please answer any of the following 22- 1 and 22-2 questions, and do one more question without scoring.
22- 1. This painting is part of the butterfly pattern. Please draw another part of the pattern to make it take L as the symmetry axis. At this time, you will get a complete pattern of a beautiful butterfly. Give it a try. (non-writing method)
22-2. The picture below shows the time displayed by the electronic clock in the mirror. When do you think the actual time should be? Draw it in the back.
5. Answer the questions. (Each small question 10, ***30)
23. The following table is a statistical table of population density in China (population density is the population per square kilometer). Please draw a statistical map, as vivid as possible. And tell me what information you can get from the picture.
Year194919591969197919891999 2003.
Population density is 57 7084102118131134.
24. Analyze the relationship between variables reflected in the figure below, imagine an actual situation suitable for it, and write it out for everyone to share.
25- 1. Xiao Ke plays games with Xiao Ai. Xiaoke has a group of cartoons, one is Mickey Mouse, and the other two are Snoopy. Let Xiao Ai draw two pictures from among them. If Mickey Mouse and Snoopy are taken away, Xiao Ai loses and Xiao Ke wins. Is the game fair? What are the chances of Xiao Ai winning?
25-2. Both China Sports Lottery and China Welfare Lottery have 3D gameplay, and the gameplay is a note by 2 yuan. If the selected three digits are the same as those drawn in the lucky draw, you will get a bonus of 1 1,000 yuan. Would you please explain the winning probability of this game with your knowledge? How many bets do I have to buy to win the prize? How to buy?
Reference answer: (There is no unique answer to the question about drawing in this answer, and this answer is for reference only)
1. Multiple choice question: CBADB BADBD
2. I will fill in:11.1612. More than 3 and less than 13 13. S = x 14。 A triangle with two equal angles is congruent.
3. Fill in the blanks:16.2mn2317. The original formula is simplified to -6x2y-2y2, and x2 is the same whether X is or-. 18.650
19.0.05438+05m2
IV.20. (The answer is not unique)
2 1.ED∨BF gets ∠ AFB = ∠ CED, AB∨CD gets ∠ A = ∠ C; Ae = cf plus EF on both sides can get af = ce. According to the corner theorem, two triangles can be congruent.
22.
( 1) (2)
V.23 (The answer is not unique)
As can be seen from the picture, the population of our country is increasing. Since 1999, population growth has been slow under the control of the state. (as long as it makes sense)
24. (The answer is not unique) Xiaoming went to school. After walking for a while, he saw an acquaintance and chatted with him for a while. He found that he was going to be late. After saying goodbye to his acquaintances, he hurried to school.
25.( 1) The game is unfair, and the probability that Xiao Ai will win is.
(2) The probability of winning the 2)3D grand prize is that if you want to win the grand prize, you must buy at least 1000, from 00 1 to 999.
A selection of easy-to-mistake questions in the first semester of senior high school (1)
Chapter V Intersecting Lines and Parallel Lines
1. The following judgment is wrong ().
A. A line segment has countless vertical lines;
B. The midpoint of line segment AB has only one straight line perpendicular to line segment AB;
C. If one of the four angles formed by the intersection of two straight lines is 90 degrees, the two straight lines are perpendicular to each other;
If two straight lines intersect, they are perpendicular to each other.
2. The following judgment is correct ().
A the vertical line from a point outside the line to the known line is called the distance from that point to the known line;
B, drawing a vertical line of a known straight line through a point outside the straight line, wherein the length of the vertical line is the distance from the point to the known straight line;
C, drawing the distance from a point outside the known straight line to the known straight line;
D. The vertical line segment is the shortest of all the line segments connecting the points outside the straight line and the points on the straight line.
3. As shown in the figure, * * in the figure has an internal angle ().
Group A.2; B.3 group; C.4 group; D.5 group
4. The following statements: ① There is only one straight line at two points; ② Two straight lines must intersect if they are not parallel; (3) One and only one straight line is perpendicular to the known straight line; (4) there is only one straight line parallel to the known straight line, and the correct one is ().
a . 1； B.2C.3d Four
5. As shown in the figure, the following reasoning is correct ().
(1) because ∠ 1 = ∠ 4, BC ∨ ad; ② Because ∠ 2 = ∠ 3, AB ∨ CD;
③ Because ∠ BCD+∠ ADC = 180, ad ∨ BC; ④ because ∠ 1+∠ 2+∠ C = 180, BC∨AD.
a . 1； B.2C.3d Four
6. As shown in the figure, for a straight line ∠ 1 = 70, find the number of times ∠2.
7. Judge whether the following statement is a proposition. If yes, please write its title and conclusion.
(1) internal dislocation angles are equal; (2) the vertex angles are equal; (3) Draw an angle of 60.
Positive solution:
(1) is a proposition. The title of this proposition is: two straight lines are cut by the third straight line; The conclusion is that the internal angles are equal. This proposition is a false proposition, that is, a false proposition.
(2) It is a proposition. The title of this proposition is: two angles are antipodal angles; The conclusion is that these two angles are equal. This proposition is a correct proposition, that is, a true proposition.
(3) Not a proposition, not a sentence to judge one thing.
8. As shown in the figure, △ a ′ b ′ c ′ is translated by △ABC. In this translation, the translation distance is line segment aa ′. Is this correct?
Chapter VI Plane Cartesian Coordinate System
1.A point coordinates meet. Try to determine the quadrant where point a is located.
2. Find the distance from point A (-3, -4) to the coordinate axis.
Chapter VII Triangle
1. As shown in the figure, in the obtuse angle △ABC, ∠B is an obtuse angle. Try to keep Gao AE on BC's side.
2. There are four line segments with lengths of 4cm, 8cm, 10cm and 12cm respectively. Choose three of them to form a triangle. How many triangles can you form?
3. How many of the three external angles of a triangle are acute angles at most?
4. As shown in the figure, in △ABC, the following statement is correct ().
A.∠ADB >∠ADE；
B.∠ADB >∠ 1+∠2+∠3；
C.∠ADB >∠ 1+∠2；
D. all of the above are true.
Positive solution: C.
Positive solution analysis: ≈ADB is an external angle of △ADC, ∴∠ ADB = ∠ 1+∠ 2+∠ 3, ∴∠ ADB > ∠ 65438.
5. If the sum of the internal angles of a polygon is 1440, find the number of sides.
These two workshops produce 680 micromotors every month as planned. Due to technical improvement, the first workshop completed the planned 120% last month, and the second workshop completed the planned 1 15%. As a result, 798 micromotors were produced in one workshop. How many micromotors were produced in each workshop last month? If two workshops each produced a micromotor meter and a meter last month, the equation set is ().
A.； b；
C.. d。
Chapter 9 Inequality and Unequal Groups
1. Using the properties of inequality to solve inequality:.
2. Does a small shop need 1m of water every day? But the waterworks only supply water once a day, so it is necessary to make a water tank to store water. It is required that the water tank is a cuboid with a bottom area of 0.8 1㎡, so how many meters high is enough? (accurate to 0. 1m)
3. A class organized 25 members to donate money to the disaster area, among which the top three were 5 people 10 yuan, 5 people 10 yuan, 2 people 5 yuan, and the rest donated 1 yuan, so the frequency of students who donated 10 yuan was _ _ _ _.
The heights of the 26 students are (height: cm):
160; 162; 160; 162; 160; 159; 159; 169; 172; 160;
16 1; 150; 166; 165; 159; 154; 155; 158; 174; 16 1;
170; 156; 167; 168; 163; 162.
Now we are going to list the frequency distribution table, please determine the starting point and point data.
Positive solution: The starting point is 149.5, which is divided into five groups: 149.5 ~ 154.5 ~ 159.5,159.5,/kloc.
Equations (groups) and inequalities (groups) are prone to errors.
Fill in the blanks
1, the solution set of inequality 2x-a≥-2 about x is as shown in the figure, so the value range of a is _ _ _ _ _ _.
2. It is known that the solution of 3(2x- 1)=2-3x is the same as the solution of equation 6-2k=2(x+3) about x, then k=_______
3, a brand of goods, sold at 20% off the list price, can still get 20% profit, if the list price of goods is 30 yuan, the purchase price is RMB.
4. It is known that the inequality about X is a one-dimensional linear inequality, then A = _ _ _ _ _ _
5, known, algebraic expression = _ _ _ _ _
6. In order to promote a certain commodity, the store will give preferential treatment to the commodity priced in 3 yuan in the following ways. If no more than 5 pieces are purchased, they shall be paid at the original price. Buy more than 5 pieces at a time, and 20% off the excess. If they spend 27. 1 yuan, they can buy at most _ _ _ _ _ _ items.
7. A said to B, "You were only 26 when I was your age, and I was 44 when you were my age." So A is _ _ _ _ _ _ _ years old and B is years old.
The sum of all integer solutions of 8 is _ _ _ _ _
9. If the solution of the equation 5x-2m=3x-6m+ 1 about x is between -3 and 3, then the value range of m is _ _ _ _ _.
10, if x > 0； in the equation; 2, y≤ 1, then the value range of m is _ _ _ _ _
1 1, if the solution set is X >；; 3, then the range of a is; If its solution set is x>a, then the value range of A is
12, if the solution set of the inequality group is-1
13, if there is no solution, the value range of a is; If there is a solution, the range of a is
14, if there is no solution, the value range of a is; If there is a solution, the range of a is
15, if there is no solution, the value range of a is; If there is a solution, the range of a is
16. It is known that the positive integer solution of the inequality 3x-a≤ 1 about X is exactly 1, 2,3,4, so the value range of a is
4. It is known that the equations about x and y are the same as the solution of, so find a and b..
5. Two students, A and B, solved the equations about X and Y. A misread the value of coefficient B and got the result. B misread the coefficient a and got the result. Please help them find the right solution.
6, a math exam, *** 16 multiple-choice questions, scoring criteria: 6 points for a question, 2 points for a wrong question, no score for answering irrelevant questions. A student has two unanswered questions. He hopes his score will be no less than 68. He answered at least a few questions correctly.
7. The solutions of equations X and Y are non-negative, so find the range of A. ..
8. A flower shop needs to cultivate two kinds of flowers and trees and three kinds of flowers and trees at a cost of 1.700 yuan. To cultivate three kinds of flowers and trees, 1 plant flowers and trees requires 1500 yuan.
(1) What is the cost of two kinds of flowers and trees?
(2) If the price of 1 plant is 760 yuan, the price of 1 plant is 540 yuan. The flower shop decided to cultivate two kinds of flowers and trees, A and B, which cost less than 30,000 yuan. If the number of flowers and trees planted by B is three times that of A, which is 10 more, and the total profit is not less than 2 1840 yuan, what specific planting plans does the flower shop have?
A selection of easy-to-mistake questions in the first semester of senior high school (2)
First, multiple-choice questions:
1. If it is known that the distance from point P(3,) to the two coordinate axes is equal, the value of is ().
A.4 B.3 C. -2 D.4 or -2
2. In the following statements: ① The point must be in the fourth quadrant; ② The points on the coordinate axis do not belong to any quadrant; ③ The point with zero abscissa is on the axis, and the point with zero ordinate is on the axis; (4) In the rectangular coordinate system, the coordinate of the point on the axis with a distance of 5 from the origin is (0,5). The correct one is ()
1。
3. It is known that the external angle is equal to twice, which is ().
A. right triangle B. acute triangle C. obtuse triangle D. isosceles triangle
4, the following statement, the correct is ()
A. The outer angle of a triangle is greater than any inner angle B. The outer angle of a triangle is equal to the sum of the two inner angles of a triangle.
C the outer corner of a triangle has at least two obtuse angles. The outer corner of a triangle has at least one obtuse angle.
5. If * * * has nine diagonals from two vertices of a polygon, then the number of sides of the polygon is ().
a6 b . 7 c . 8d . 9
6. If a polygon * * * has 27 diagonals, then the number of sides of the polygon is ().
a6 b . 7 c . 8d . 9
7. If each outer corner of a polygon is an acute angle, the number of sides of the polygon shall not be less than ().
a3 b . 4 c . 5d . 6
8, regular pentagon * * * axis of symmetry is ()
A.2 Article B.4 Article C.5 Article D. 10/0
9, known, if, the relationship between x and y is ()
The CBI is not sure.
10. If the sum of other internal angles of a polygon is 257, the internal angle is equal to ().
a . 90 b . 105 c . 148
14, the sum of two digits of a ten-digit number and a one-digit number is 7. If you add 45 to this two-digit number, it just becomes a two-digit number after the one-digit number and the ten-digit number are reversed, then this two-digit number is ().
a . 16b . 25c . 38d . 49
15, the waist length of an isosceles triangle is 4cm, so its base length can't be ().
A. 1 cm b. 3 cm c. 6 cm d. 9 cm
16. Among the following conditions, the condition that does not necessarily make two triangles congruent is ().
A. the two angles are equal. B. the two angles are equal.
C. tripartite equality. Two sides are equal to their included angle.
Second, fill in the blanks
1, point p is in the second quadrant, then q is in the fourth quadrant.
2. If a point is translated by 2 units to the right and then by 3 units to the down, the obtained point is the coordinate origin, and the coordinates of the point are
3. When drawing human body sketch in art class, Chen Cheng draws the bridge of the nose on the axis of rectangular coordinate system. If the right eye coordinate is (2,5), the left eye coordinate is
4. If one side of an isosceles triangle is 10㎝ and the other side is 6㎝, then its circumference is.
A big mirror was set up at the sharp turn of an expressway, and the car number seen from the mirror is as shown in the figure.
As the picture shows, the number of the car is.
6. In a pentagon, the ratio of the first four angles is 1: 2: 3: 4, and the fifth angle is more than the minimum angle 100, so the five internal angles of the pentagon are _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
7.In, D and E are points on AB and AC respectively, and BE and CD intersect at F and if.
Then,
8. As we all know, the outer angle of an isosceles triangle is equal to, then its base angle is equal to.
9. In the internal angle of a convex polygon, there is at most one acute angle.
10, every inner angle of a convex polygon is equal to 140, so there is a diagonal line from a vertex of this polygon.
1 1, the nonnegative integer solution satisfied is
The satisfactory integer solution is
12, known, size is
Given, the size of is
13, known, please arrange "
14, given that the solution of the equation is the smallest integer solution of the inequality, then the algebraic expression
15, the following statements: ① If, then; 2 If, then; 3 If, then; 4 if, then; ⑤ If, then; 6 If, then; ⑦ If, then.
What is correct is that
16, known, if, the value range of is
17, one exam * * *, there are 5 questions, and if you do the right question of 1, you get 1 point. It is known that the average score of 26 people exceeds 0, of which 3 people have 4 points, the lowest is 3 points, and some people have 5 points.
A teacher was asked how many students were in his class. The teacher said, "Half of the students are studying math, one quarter are studying music, one seventh are studying foreign languages, and less than six students are playing football on the playground." So, there are students in this class.
19, if known, the value range is
20. If the lengths of the three sides of a triangle are respectively, the value range of is
2 1, when the algebraic solution set is
22, an isosceles triangle, the circumference is, from a vertex on the bottom to the midline of the waist, divided into two parts, one part is longer than the other part, then the waist length is
23, if, about the solution of binary linear equations is reciprocal, then
24. If AC, BD and EF are equally divided at point O, then all congruent triangle pairs in the graph.
25. If a straight line represents three intersecting expressways, it is necessary to build a cargo transfer station now, and ask it to have the same distance to the three expressways, so that there is a place to choose.
26. In, AD divides BC equally in D and E. If so, the circumference is
Third, answer questions:
1. If the inequality group has a solution, try to judge the solution of the inequality group.
2. Given a set of equations, (1) if the solution of the set of equations is positive, the required range of values;
(2) If the solution of the equation is satisfied, the range of values to be found.