1.( 1)-2km (2) zero plus 5 +5 minus 3 -3 (3) loss.

2. Solution: (1) The benchmark is 12 noon, which is 0h, negative before noon and positive after noon. 2 hours before noon means -2 hours and 3 hours after noon means +3 hours.

(2) The benchmark is the water level of the day, and it is recorded as 0cm. The water level one day ago was positive, and the water level one day later was negative. +2cm one day ago and -2cm one day later.

Answers to the seventh grade math textbook Shanghai Education Edition (2) Exercise 1. 1

1.( 1)-40 (2) clockwise 2 (3) is less than 0.02.

2. Solution: 08 national debt 0 1 neither rises nor falls on the same day; 08 national debt 02 fell 0.05 yuan on the same day; 08 Treasury bonds fell on the day of 03 1.24 yuan; 09 Anhui debt 0 1 rose 0. 15 yuan on the same day; 09 Shanghai debt 0 1 fell 2.0 1 yuan on the same day.

3. Solution: 1.2mm indicates that the standard thickness of optical disc is 1.2mm, and 0. 1mm indicates the allowable fluctuation range of optical disc thickness, that is, the maximum thickness of optical disc is not more than1.2+0.1=1.

4. Solution: Take the lakeside dike as an example? Benchmark? , that is, 0m. If the height above the lakeside dike is positive, the height of the top of the building near the lake can be expressed as 20-4= 16(m), that is, 16m (or+16m), and the sunken depth is -(4+8)=- 12(m).

5. Solution: The increase amounts are 14.9, -4.9, 19.8, -6 1.2, -53.5 and -7.7. When the increase is negative, it actually decreases.

6. Solution: positive integer: 8,302,28;

Negative integers: -207,-79;

Positive score:1/32; 42.5, 13/25;

Negative scores: -8.34, -4/5, -6.5.

There is a number that is neither positive nor negative. It is 0.

7. Solution: Integer: {-9,2,+1, -2}

Score: {-0. 1. 1/2, -5/2, 3.5}

Positive numbers: {1/2,2,+1, 3.5}

Negative numbers: {-0. 1, -9, -5/2, -2}

The seventh grade mathematics textbook answers Shanghai Education Edition (3) Exercise 1.2

1. Solution: Their antonyms are 1/2, 0.6 1,-16, -8 and -2.5 respectively.

2. Solution: The answer is not unique. For example, +5, -3,-1.5; The antipodal of +5 is -5, the antipodal of -3 is +3 and the antipodal of-1.5 is+1.5. This is shown on the number axis of fig. 3.

3. Solution: As shown in Figure 4, points A and B represent numbers with an absolute value of 3, points C and D represent numbers with an absolute value of 1.5, and point E represents numbers with an absolute value of 0.

4. Solutions: -5 and-1.

5. Solution: the equivalent is (1)(3) and the inverse is (2)(4).

6. Solution: The absolute values are 25, 0.08, 7, 1.5, 0, 9/1.

7. There are two solutions: (1), namely +5 and -5.

② From 1.

(3) does not exist, because the absolute value is non-negative, that is |a|? 0.

8. Solution: Based on the design length, the difference between the measured values and the design length is represented by positive and negative numbers, namely: +4, +2,-1, -3, -2. The result measured for the third time is the closest to the design length, and the absolute value of the difference between the data measured for the third time and the design length is the smallest.