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沪科版七年级上册数学书习题1.4答案

1习题1.4第1题答案

(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习题1.4第2题答案

(1)(-8)-(+3)=(-8)+(-3)=-(8+3)=-11

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

(3)3—8=3+(+8)=+(8+3)=11

(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)=61/2

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

(9)40-41=40+(-41)=-(41-40)=-1

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

3习题1.4第3题答案

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

(2)(-41)+(+30)+(+41)+(-30)=-41+30+41-30=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习题1.4第4题答案

(1)(1-2)+(3-4)+(-5+6)=(-1)+(-1)+(-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)=3/4-11/6+(-1/6)=3/4+(-11/6)+(-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习题1.4第5题答案

(1)x=-7

(2)x=-2

6习题1.4第6题答案

(1)错误.如两个负数相加

(2)错误.如(-2)-(-5)>-2

(3)错误.如(+5)+(+2)=+3

(4)正确

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