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1. 写成省略加号和括号的形式后为$-5 -7 -2 +9$的式子是 （
A.$(-5)-(+7)-(-2)+(+9)$
B.$-(+5)-(-7)-(+2)-(+9)$
C.$(-5)+(-7)+(+2)-(-9)$
D.$-5-(+7)+(-2)-(-9)$
D
）A.$(-5)-(+7)-(-2)+(+9)$
B.$-(+5)-(-7)-(+2)-(+9)$
C.$(-5)+(-7)+(+2)-(-9)$
D.$-5-(+7)+(-2)-(-9)$
答案
1.D
2. 下列等式成立的是 （
A.$3-(-4)+(-5)=3-4+5$
B.$3+(-4)+(-5)=3-4+5$
C.$3+(-4)-(-5)=3-4+5$
D.$3-(-4)-(-5)=3-4+5$
C
）A.$3-(-4)+(-5)=3-4+5$
B.$3+(-4)+(-5)=3-4+5$
C.$3+(-4)-(-5)=3-4+5$
D.$3-(-4)-(-5)=3-4+5$
答案
2.C
3.把下列各式写成省略加号和括号的形式：
(1) $6+(+3)+(-7)-(-2)=$
(2) $(-8)-(-1)+(+3)-(-2)=$
(3) $-6-(+7)+(-2)-(-9)=$
(4) $(+8)+(+3)+(-2)-(-6)=$
(1) $6+(+3)+(-7)-(-2)=$
6+3-7+2
；(2) $(-8)-(-1)+(+3)-(-2)=$
-8+1+3+2
；(3) $-6-(+7)+(-2)-(-9)=$
-6-7-2+9
；(4) $(+8)+(+3)+(-2)-(-6)=$
8+3-2+6
.答案
3.(1)$6+3-7+2$ (2)$-8+1+3+2$ (3)$-6-7-2+9$ (4)$8+3-2+6$
4. 计算:
(1) $(-\dfrac{1}{3})-15+(-\dfrac{2}{3})$;
(2) $+14-10-(-9)+(-5)$;
(3) $0-(+8)+(-27)-(+5)$;
(4) $2.7+(-8.5)-(+3.4)-(-1.2)$;
(5) $(-\dfrac{3}{4})+(-\dfrac{2}{3})+(-\dfrac{1}{4})+\dfrac{2}{3}$;
(6) $-\dfrac{1}{3}+(-\dfrac{5}{6})-(-\dfrac{1}{4})-0.5$.
(1) $(-\dfrac{1}{3})-15+(-\dfrac{2}{3})$;
(2) $+14-10-(-9)+(-5)$;
(3) $0-(+8)+(-27)-(+5)$;
(4) $2.7+(-8.5)-(+3.4)-(-1.2)$;
(5) $(-\dfrac{3}{4})+(-\dfrac{2}{3})+(-\dfrac{1}{4})+\dfrac{2}{3}$;
(6) $-\dfrac{1}{3}+(-\dfrac{5}{6})-(-\dfrac{1}{4})-0.5$.
答案
4.(1)$-16$ (2)$8$ (3)$-40$ (4)$-8$ (5)$-1$ (6)$-\dfrac{17}{12}$
5. 能与$-(\dfrac{1}{2}-\dfrac{2}{3})$相加得0的数是 （
A.$-\dfrac{1}{2}-\dfrac{2}{3}$
B.$-\dfrac{1}{2}+\dfrac{2}{3}$
C.$\dfrac{1}{2}+\dfrac{2}{3}$
D.$-\dfrac{2}{3}+\dfrac{1}{2}$
D
）A.$-\dfrac{1}{2}-\dfrac{2}{3}$
B.$-\dfrac{1}{2}+\dfrac{2}{3}$
C.$\dfrac{1}{2}+\dfrac{2}{3}$
D.$-\dfrac{2}{3}+\dfrac{1}{2}$
答案
5.D
