1, introducing negative numbers is a practical need, so we use
straight
Numbers to represent the opposite quantity. For quantities with opposite meanings, we can define one of them as
positive number
The opposite amount is.
negative number
2. If the water level drops by 3 meters and is marked as -3 meters, it will rise by 4 meters.
+4
, not rising but falling.
3. If the instrument rotates 45 clockwise and records it as-45, the meaning of 120 is
Turn counterclockwise 120.
4. A classmate scored 57 points, 78 points, 90 points and 60 points in three exams. Please use positive and negative numbers to indicate that the passing score of this student is.
-3
+ 18
+30
20 meters south means
Go north for 20 meters
6. The actual meaning of expenditure-130 yuan If the income is positive.
Income 130 yuan
8. Only
Different symbols
The two numbers of are called antonyms, and the antonym of 0 is
10. If two numbers are opposite, their sum is.
1 1, if a =-4, then -a =
four
; If -x= 3. 1, then x=
-3. 1
The absolute values of 12 and -5 are
five
The absolute value of 10. 1 is
10. 1
The absolute value of 0 is
The number with an absolute value of 3 is
-3 or +3
, 12 and
- 12
The absolute values of are equal.
13, specifies the number axis.
Origin, positive direction and unit length
On the number axis, -3 is the origin.
left
Edge, -2.5 at-3
correct
Edge.
14, the number represented by two unit lengths from the origin on the number axis is
Plus or minus 2
The reciprocal of 15 and a is _ _-A _ _, and the reciprocal of a number is the smallest positive integer, so this number is _ _- 1 _ _.
16, the rational number with the smallest absolute value is _ __0 _ _ _, and the integer with the absolute value less than 3 is _ _ 0, 1, 2 _ _ _ _.
Negative integers with absolute values greater than 1 less than 5 are _ _ _ _ _ _ _-2, -3,-4 _ _ _ _ _ _ _.
The absolute value of 18, _ _1_ _ _ is equal to the absolute value of its reciprocal.
19. It is known that 2a and 3-a are reciprocal, so a = _ _ _ _1_ _ _.
20. if a and b are reciprocal, and c and d are reciprocal, then A-CD+B = _ _- 1 _ _, 3a+4cd+3b=__+4__.