1. Hint: 5,-1, 3, 2.6,-1.2, 0.9,-1/2.

2.( 1)2.8 -3.2 (2)+4 -7 (3)-8 9

3.C

Shanghai Science Edition (II) Answers to Grade 7 Mathematics Textbook 1 1 Page

1. solution: as shown in figure 2. |-4|=4,|+3/2|=3/2,|-2|=2,|0|=0,|3.2|=3.2,|-0.5|=0.5,|7|=7

2.3 1.5 0 5 0.02 3/4 1/6 100

3. Solution: (1) |-8 |+9 | = 8+9 = 17.

(2)|- 12|? | 12|= 12? 12= 1

(3)|0.6|-|-3/5|=|0.6|-|-0.6|=0.6-0.6=0

(4)|-3|? |-2|=3? 2=6.

4.D

5. Solution: |8|=8, |-8|=8, | 1/4|= 1/4, |- 1/4|= 1/4.

Answers to the seventh grade mathematics textbook of Shanghai Science Edition (3) Exercise 1.4

1. Solution: (1) (-17)+(+6) =-(17-6) =-11.

(2)(+23)+(- 18)=+(23- 18)=5.

(3)(- 12)+(-4)=-( 12+4)=- 16 .

(4)(+4)+(+8)=+(4+8)= 12.

(5)(-0.9)+(-2. 1)=-(2. 1+0.9)=-3.

(6)(-20 )+0=-20.

(7)(-2/3)+(+2/3)=0.

(8)2/5+(- 1/3)=+(6/ 15-5/ 15)= 1/ 15.

2. Solution: (1) (-8)-(+3) = (-8)+(-3) =-(8+3) =-1.

(2)(-3)-(-5)=(-3)+(+5)=+(5-3)=2.

(3)3? 8=3+(+8)=+(8+3)= 1 1.

(4)3-(-5)=3+(-5)=-(5-3)=-2.

(5)0- 18=0+(- 18)=- 18.

(6)(- 15)- 15=- 152+(- 15)=-30.

(7)(+33/4)-(-2 3/4)=(+3 3/4)+(+2 3/4)=6 1/2.

(8)(-3.6)-(-2.4)=-3.6+(+2.4)=-(3.6-2.4)=- 1.2.

(9)40-4 1=40+(-4 1)=-(4 1-40)=- 1.

( 10)(-2.2)-(-2.2)=-2.2+(+2.2)=0.

3. Solution: (1) 5+(-6)+3+8+(-4)+(-7) = 5-6+3+8-4-7 =-1.

(2)(-4 1)+(+30)+(+4 1)+(-30)=-4 1+30+4 1-30=0.

(3)(-0.8)+ 1.2+(-0.7)+(-2. 1)+0.8+3.5=-0.8+ 1.2-0.7-2. 1+0.8+ 3.5= 1.9.

(4)-7/2+8/3- 16/9+3/2=-7/2+3/2+(8/3- 16/9)=-2+ 8/9=- 1 1/9 .

(5)-8+ 12- 16-23=-(8+ 16+23)+ 12=-35 .

(6)- 1/4+5/6+2/3- 1/2=-3/ 12+ 10/ 12+8/ 12-6/ 12=9/ 12=3/4.

4. Solution: (1) (1-2)+(3-4)+(-5+6) = (-1)+=-3.

1-2+3-4+5+6=( 1+3+5)-(2+4+6)=9- 12=-3.

(2)-(8- 12)+(- 16+20)=-(-4)+4=4+4=8;

-8+ 12- 16+20=( 12+20)-(8+ 16)=32-24=8.

(3)3/4-(5/2-2/3)+(-5/3)+(3/2)=3/4- 1 1/6+(- 1/6)=3/4+(- 1 1/6)+(- 1/6)=- 1 1/4;

3/4-5/2+2/3-5/3+3/2=3/4+(-5/2+3/2)+(2/3-5/3)=3/4+(- 1)+(- 1)=- 1 1/4.

5. Solution: (1)x=-7. (2)x=-2。

6. Solution: (1) error, such as the addition of two negative numbers.

(2) Error. For example, (-2)-(-5)>-2.

(3) error. For example, (+5)+(+2)=+3.

(4) correct.

7. Solution: This question is open-ended, and the answer is not unique.

Such as (1) (-2)+(+3) >; (-2)-(+3)

(2)(-2)+(-3)& lt； (-2)-(-3).

(3)(-2)+0=(-2)-0.

8. Solution: Because |a|=8 and |b|=5, so a=? 8，b=？ 5. Because A+B > 0, so a=8, b=5, or a=8, b=-5, so a-b=3 or 13.

9. Solution: (1) (-7)+(+4)+(+8)+(-3)+(+10)+(-3)+(-6)+(-12) A: After completing 10 times, this police car is on the left side of M station, 3 kilometers away from M station.

(2) The total distance of this police car is |-7 |+|+4 |+|+8 | |-3 |+|10 |+|-3 |+|-6 |+|-12 |+9 | |-3. ( 1 1? 100)=7. 15(L)。 A: * * * consumed 7. 15 liter of engine oil this morning.