_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Class (in English)
First, multiple-choice questions (3 points for each question, * * * 36 points)
1. In, +7, 0, and positive numbers have ().
a， 1 b，2 c，3 d，4
2. Among the following logarithms, the one with equal value is ().
A.-27 and (-2)7 B- 32 and (-3) 2
C.-3×23 and -32× 2 D.-(-3) 2 and -(-2) 3
3. Among -5, -3.5, -0.0 1, -2, -2 12, the largest number is ().
A.- 12 B. - C. -0.0 1 D. -5
4. () The following statement is true ()
5. The absolute value is greater than or equal to 1, and the sum of all positive integers less than 4 is ().
A.8 B.7 C.6 D.5
6. If the reciprocal of a number is known as, then this number is ().
A.B. C. D。
7, as shown in the figure, then the following conclusion is correct ()
A is bigger than b, and b is bigger than a.
C.A. is as big as B. The sizes of D.A. and B are uncertain.
8. If the sum of the squares of a number is equal to 0, then the number can only be ().
A.0b.- 1 c. 1 d.0 or 1
9. The Yangtze River, the longest river in China, is about 6,300 kilometers long, which is expressed by scientific notation as ().
a . 63× 102km b . 6.3× 102km。
C.6.3× 104 km
10, the following operation is correct ()
A.-22= 4 years BC.
1 1, the following operation process is correct ()
a 、=… B.=…
c 、=… D.=…
12, the following judgment is correct ()
A. two negative rational numbers, the big one is far from the origin b and is positive.
C. two rational numbers, the one with the largest absolute value is far from the origin d .- is a negative number.
II. Fill in the blanks (3 points for each question, * * * 24 points)
13. On the number axis, the number represented by the point from point 4 representing -5 is.
14, the absolute value of a number is 5, then this number is.
15, fill in the blanks as required: 1347.56≈ (accurate to 0.1); 0.0 10253≈ (four significant figures are reserved).
16, use ∞ to define a new operation: for any real numbers A and B, there is a ☆ B = B2+ 1. For example,1☆ 4 = 42+1=17, then 1 ☆ 3. When m is an arbitrary rational number, m ☆ (m ☆ 2) =.
17. the storage unit of the computer is: byte b, kilobyte KB, megabyte MB: 1MB = 1024 KB.
1KB= 1024B, two bytes are equivalent to one Chinese character, so how many Chinese characters can be stored on a floppy disk of 1.44MB at most, and it is expressed by scientific counting method (three significant figures are reserved).
18. if a and b are reciprocal, and c and d are reciprocal, the algebraic expression 2ab-(c+d)+= _ _ _ _.
19, if, then x+y =.
20. The words (25 0.1) kg, (25±0.2)kg and (25±0.3)kg were marked on the flour bags of three brands sold in a grain store, and two bags were randomly taken out, and the difference between them was at most kg.
Third, answer questions.
2 1. Calculation (***20 points)
⑴.32( 1)+(-2( 1))-(- 3( 1))+23(2) (2).(3(2)-4( 1)-8(3)+24(5))×48
(3).(4)
22.( 10) The meteorological observation data of a sounding balloon shows that the temperature drops by about 6℃ every time the altitude increases by 1 km. If the ground temperature is 2 1℃ and the temperature somewhere in the sky is -39℃, what is the altitude here?
23. For any nonzero rational numbers A and B, the definition operation is as follows:
The value. (This question 10)
24.( 10) Observe the following equation.
,,,
Add the two sides of the above three equations respectively to obtain:
.
(1) Guess and write. (2 points)
(2) Write the following calculation results directly: (4 points)
① ;
② .
(3) Inquiry and calculation: (6 points)
25.( 10) The positions of known rational numbers A, B and C on the number axis are as shown in the figure, and
(1) for value.
② Simplify.