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50 easy-to-mistake problems in mathematics in the first semester of junior one.
1._ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ is called a positive number.

2. If "-2" is compared with a number 2 less than 95, "+1" means _ _ _ _, and "-5" means _ _ _ _.

3. An elevator apartment has 24 floors, 22 floors above ground and 2 floors underground. If someone takes the elevator from the second floor underground to the eighth floor above ground, the elevator will go up by _ _ _ _.

4. The following judgment is correct ()

1 +a is a positive number 2 -a is a negative number 3a >;; 0 4 a & lt0

A. 1、2

B.3、4

C. 1、2、3、4

D. None of them are correct.

5. The classroom is 2.8m high and the desks are 0.6m high. If the desktop is 0 meters, what is the top and bottom of the classroom? How far is the top of the classroom from the ground? If the top is 0 meters, what is the height of the desktop and the ground?

6. A negative score must be a negative rational number (judgment) ()

7. It is known that the distance from a point on the number axis to the origin is 2, so the number represented by a point with a distance of 3 on the number axis is ().

1。

8. The three elements of the number axis are _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

9. If |a|=4, |b|=3, and a

10. The absolute value of _ _ _ is itself, and the absolute value of _ _ _ is its reciprocal.

1 1. If a is positive, | a | = _ _ _ If a is negative, | a | = _ _ _

12. If the absolute values of two numbers are equal, then these two numbers ()

A. Equality B. Both of them are 0 C. Opposed to each other D. Equal or opposed to each other 13. Find the minimum value of |x- 1|+|x-2| on the number axis.

14.a\b is the reciprocal, c\d is the reciprocal, and |m|=2. What is the value of (a+b)/m- 1+m-cd?

15. The sum of all integers whose absolute value is not greater than 3 is _ _ _

16. The sum of negative integers with absolute values less than 5 is _ _ _ _ _

17.a+b-c+a-c+b=a-__+__

18. When calculating 4 1+a, mistake "+"for "-"and the result is-12, then the value of 4 1+a is _ _ _.

19. if a> 1, then | a-1| = _ _ _ if a

20. The number less than A -3 is _ _ _

2 1. The following are known:

A number whose absolute value is equal to itself has countless opposites, and a number equal to itself is only 0.

The number whose reciprocal equals itself is only 1. There are three numbers whose square is equal to itself.

There are () kinds of correct statements (fill in the options).

A. 1

22.(- 10.2)+(-3.5)=

23. (Difficulty)-(A+B) = _ _ _ _ _ (Requirements: Simplified)

24. (key) if a> 1, simplified form: |1-a | = _ _ _ _ _ _

1. Choose carefully: (30 points for this question, 3 points for each small question)

1. Among the following four graphics, what you can't get from translating the basic graphics is

2. There are five pieces of wood with lengths of 12cm, 10cm, 8cm, 6cm and 4cm respectively. The probability that any three pieces of wood can form a triangle is ().

A.B. C. D。

3.sum is the solution of equation y=kx+b, so the values of k and b are () respectively.

A.- 1.3 b . 1.4 c . 3,2 D.5,-3

4. It is known that a ship has a deadweight of 600 tons and a volume of 2400m3. Now we have to load two kinds of goods, with a volume of 7m3 per ton and a volume of 2m3 per ton. How to load the cargo can make the best use of the load and volume of the ship. If the goods A and B are x tons and y tons respectively, then the equations can be ().

A.B. C. D。

5. The following proposition is true ()

A. congruence of two triangles with equal areas;

B. All equilateral triangles are congruent;

C. Two triangles with equal angles between two sides;

D, two triangles corresponding to two sides and an angle are congruent.

6. The following proposition is true ()

The bisector, midline and height of triangle A are all within the triangle; B. A right triangle has only one height.

At least one height of the triangle is within the triangle; All three heights of an obtuse triangle are outside the triangle.

7. In △ABC, if ∠ A = 70-∠ B, ∠C = ().

Answer. 35 b . 70 c . 1 10d . 140

8. It is impossible to roll two dice at the same time. The event is ()

A, the sum of points is less than 4 B, the sum of points is greater than 13 C, the sum of points is even d, and the sum of points is odd.

9. As shown in the figure, in △ABC, AD is the angular bisector and AE is high.

Given ∠BAC=2∠B and ∠B=2∠DAE, ∠ACB is (▲).

Answer. 80 B.72

C.48 D、36

10. If 5x3m-2n-2yn-m+1= 0 is a binary linear equation, then the values of m and n are () respectively.

A.2,3 B.2, 1 C

1 1. There are 25 boys and 24 girls in Class 1, Grade 7 in a school. If you choose one, the probability of choosing a boy is ().

0 BC

12. The transformations between the following three groups of two graphs belong to () respectively.

A. Translation, rotation and rotation B. Translation, axial symmetry and axial symmetry

C. Translation, axis symmetry and rotation D. Translation, rotation and axis symmetry

13. Among the three internal angles of the triangle ()

I don't know if it's ok.