1. If both A and B represent rational numbers and A+B = 0, then ()

A.a and b are both 0.b.a, and one of b is 0. C.A. and B are opposites, and D.A. and B are reciprocal.

2. The following statement is true ()

A. single item and the sum of single items are single items. B. the sum of a single term and a single term is a polynomial.

C. the sum of polynomials is polynomials. D. the sum of algebraic expression and algebraic expression is algebraic expression.

3. The following statement is incorrect ()

A. there is the smallest natural number. B. there is no minimum positive rational number.

C. there is no largest negative integer. D. there is no maximum non-negative number.

4. If A and B represent rational numbers, and the value of a+b is greater than that of a-b, then ().

A. a. b with the same number. B.a., b with different numbers. c.a > 0.d.b > 0。

5. An integer greater than-π and not a natural number is ()

A.2.B.3.C.4.D is numerous.

6. There are four kinds of statements:

A. the square of a positive number is not necessarily greater than itself; The cube of b positive number is not necessarily greater than itself;

C. the square of a negative number is not necessarily greater than itself; D. the cube of a negative number is not necessarily greater than itself.

Among these four statements, the incorrect statement is ()

A.0.b. 1.c.2.d.3

7.A stands for rational number, so the relationship between A and -A is ().

A greater than -a b less than -a c greater than -a or A less than -a d a is not necessarily greater than -a.

8. In the process of solving the equation, in order to make the obtained equation and the original equation have the same solution, you can add () on both sides of the original equation.

A. multiply by the same number. B. Multiply the same algebraic expression. C. add the same algebraic expression. D. add 1.

9. There was more than half a glass of water in the cup, which decreased by 10% on the second day and increased by 10% on the third day. So, the comparison result between the water in the cup on the third day and the first day is ().

A. as much as B.

10. This ship goes back and forth between two docks of a river. If the speed of the ship itself in still water is fixed, then when the flow speed of the river increases, the time it takes for the ship to make a round trip will be ().

A. increase. B. reduce. C. unchanged. D. increase and decrease are possible.

II. Fill in the blanks (each question 1 point, * * *1point)

1.______.

2. 1989 19902- 1989 19892=______.

3.=________.

4. The solution of the equation about X is _ _ _ _ _ _ _.

5. 1-2+3-4+5-6+7-8+…+4999-5000=______.

6. When x=-, the value of algebraic expression (3x3-5x2+6x-1)-(x3-2x2+x-2)+(-2x3+3x2+1) is _ _.

7. When a =-0.2 and b=0.04, the value of algebraic expression is _ _ _ _ _.

8. There is 60 kilograms of salt water with 30% salt, which is evaporated on the scale. When salt water becomes 40% salt, the weight of salt water is _ _ _ _ _ grams.

9. A batch of parts can be manufactured in 0/8 days as planned. If the work efficiency is improved after 4 days, it will take _ _ _ _ _ days to complete half of this batch of parts.

10. It's 4: 05 now, and in _ _ _ minutes, the minute hand and the hour hand will coincide for the first time.

Answers and tips

First, multiple choice questions

1.C 2。 D 3。 C 4 explosive D 5。 C 6。 B 7。 D 8。 D 9。 C 10。 A

Tip:

1. Let a=2, B =-2, and satisfy 2+(-2) = 0, thus

2.x2, 2x2 and x3 are all monomials. The sum of two monomials x3 and x2 is x3+x2 is a polynomial, excluding A. The sum of two monomials x2 and 2x2 is x3-x2 is a monomial, excluding B. The sum of two polynomials x3+x2 and x3-x2 is 2x3 is a monomial, so we choose D. 。

3. 1 is the smallest natural number, and A is correct. You can find the positive side.

Therefore, the statement that C "has no maximum negative integer" is incorrect. Write the expanded natural sequence, 0, 1, 2, 3, …, n, …, and it is easy to know that there is no largest non-negative integer and d is correct. Therefore, the incorrect statement should be C.

5. On the number axis, it is easy to see that there are only four integers -3, -2,-1, 0 * * * to the right of-π and to the left of 0 (including 0). Choose C.

6. From 12= 1, 13= 1, we know that A and B are correct. From (-1) 3 =- 1, we know that d is also correct. The squares of negative numbers are all positive numbers, that is, negative numbers.

7. If a=0, you can immediately exclude A, B, C and choose D..

8. For the deformation of the same solution of the equation, both sides of the equation are required to be multiplied by a number that is not equal to 0. So we ruled out a.

When we consider the equation X-2 = 0, it is easy to know that its root is x=2. If both sides of the equation are multiplied by an algebraic expression X- 1, we get (X- 1) (X-2) = 0, its root is x= 1, and x=2. If it is not the same solution of the original equation, B is excluded.

9. Let the original amount of water in the cup be A, which can be obtained according to the meaning of the question.

The next day, the amount of water in the cup is a× (1-10%) = 0.9a;

On the third day, the amount of water in the cup is (0.9a) × (1+10%) = 0.9 ×1.1× a;

The ratio of water in the cup on the third day to that in the first day.

So on the third day, there was less water in the cup than on the first day, so C was chosen.

10. Suppose the distance between two docks is s, the speed of the ship in still water is A, the water speed is v0, and the round-trip time is

Let the river speed increase to v, and (V > v>v0), and the time for a round trip is

Because v-v0 > 0, a+v0 > a-v0, a+v > a-v.

So (a+v0) (a+v) > (a-v0) (a-v)

∴ t0-t < 0, that is, t0 < T. Therefore, it takes more time to increase the river speed, so choose A. 。

Second, fill in the blanks

Tip:

2. 1989 19902- 1989 19892

=( 1989 1990+ 1989 1989)×( 1989 1990- 1989 1989)

=( 1989 1990+ 1989 1989)× 1=39783979.

3. Because (2+1) (22+1) (24+1) (28+1) (216+1).

=(2- 1)(2+ 1)(22+ 1)(24+ 1)(28+ 1)(2 16+ 1)

=(22- 1)(22+ 1)(24+ 1)(28+ 1)(2 16+ 1)

=(24- 1)(24+ 1)(28+ 1)(2 16+ 1)

=(28- 1)(28+ 1)(2 16+ 1)

=(2 16- 1)(2 16+ 1)=232- 1.

2 ( 1+x)-(x-2) = 8，2+2x-x+2 = 8； x=4

5. 1-2+3-4+5-6+7-8+…+4999-5000

=( 1-2)+(3-4)+(5-6)+(7-8)+…+(4999-5000)

=-2500.

6.(3x 3-5x 2+6x- 1)-(x3-2 x2+x-2)+(-2 x3+3 x2+ 1)= 5x+2

7. Takes note of:

When a =-0.2 and b=0.04, A2-B = (-0.2) 2-0.04 = 0, B+A+0.16 = 0.04-0.2+0.16 = 0.

8.60× 30% (kg) salt water with a salt content of 30% is changed into x grams of water with a salt content of 40% by evaporation, that is, 0.00 1x kg. At this time, 60×30% = (0.00 1x) × 40%.

Solution: x=45000 (grams).