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
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
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
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
习题1.4第5题答案
(1)x=-7
(2)x=-2
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