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1. (教材例题变式)把$(-2)-(+3)-(-5)+(-4)$统一为加法运算,正确的是（
A.$(-2)+(+3)+(-5)+(-4)$
B.$(-2)+(-3)+(+5)+(-4)$
C.$(-2)+(+3)+(+5)+(+4)$
D.$(-2)+(-3)+(-5)+(+4)$
B
）A.$(-2)+(+3)+(-5)+(-4)$
B.$(-2)+(-3)+(+5)+(-4)$
C.$(-2)+(+3)+(+5)+(+4)$
D.$(-2)+(-3)+(-5)+(+4)$
答案
1.B
2. 为计算简便，把$(-5)-(-4)-(+3)+(+2)+(-1)$写成省略括号的形式是（
A.$-5-4-3+2-1$
B.$-5+4-3+2-1$
C.$-5+4+3+2-1$
D.$-5-4+3+2+1$
B
）A.$-5-4-3+2-1$
B.$-5+4-3+2-1$
C.$-5+4+3+2-1$
D.$-5-4+3+2+1$
答案
2.B
3. 下列交换加数的位置的变形中,正确的是
（
A.$1-4+5-4=1-4+4-5$
B.$-\dfrac{1}{3}+\dfrac{3}{4}-\dfrac{1}{6}-\dfrac{1}{4}=\dfrac{1}{4}+\dfrac{3}{4}-\dfrac{1}{3}-\dfrac{1}{6}$
C.$1-2+3-4=2-1+4-3$
D.$4.5-1.7-2.5+1.8=4.5-2.5+1.8-1.7$
（
D
）A.$1-4+5-4=1-4+4-5$
B.$-\dfrac{1}{3}+\dfrac{3}{4}-\dfrac{1}{6}-\dfrac{1}{4}=\dfrac{1}{4}+\dfrac{3}{4}-\dfrac{1}{3}-\dfrac{1}{6}$
C.$1-2+3-4=2-1+4-3$
D.$4.5-1.7-2.5+1.8=4.5-2.5+1.8-1.7$
答案
3.D
4. 把下列各式写成省略括号的形式：
(1)$5+(-3)-(-7)-(+2)=$
(2)$(-8)-(+4)+(-5)-(-2)=$
(3)$-6-(+7)+(-2)-(-9)=$
(4)$(+8)+(+3)+(-2)-(-6)=$
(1)$5+(-3)-(-7)-(+2)=$
5-3+7-2
；(2)$(-8)-(+4)+(-5)-(-2)=$
-8-4-5+2
；(3)$-6-(+7)+(-2)-(-9)=$
-6-7-2+9
；(4)$(+8)+(+3)+(-2)-(-6)=$
8+3-2+6
.答案
4.(1)5-3+7-2 (2)-8-4-5+2 (3)-6-7-2+9 (4)8+3-2+6
5. 把下列各式先改写成省略括号的形式，再进行计算：
(1)$(-5)-(+7)-(-6)+4$；
(2)$23-17-(-7)+(-16)$；
(3)$(-2.4)-(+1.6)-(-7.6)-(-9.4)$；
(4)$(-7)-(-4)-(+9)+(+2)-(-5)$；
(5)$(+\dfrac{2}{3})+(-\dfrac{4}{5})-(+\dfrac{1}{5})-(-\dfrac{1}{4})-(+1)$；
(6)$(-4\dfrac{7}{9})-(-3\dfrac{1}{5})-(+2\dfrac{2}{9})+(-6\dfrac{1}{5})$.
(1)$(-5)-(+7)-(-6)+4$；
(2)$23-17-(-7)+(-16)$；
(3)$(-2.4)-(+1.6)-(-7.6)-(-9.4)$；
(4)$(-7)-(-4)-(+9)+(+2)-(-5)$；
(5)$(+\dfrac{2}{3})+(-\dfrac{4}{5})-(+\dfrac{1}{5})-(-\dfrac{1}{4})-(+1)$；
(6)$(-4\dfrac{7}{9})-(-3\dfrac{1}{5})-(+2\dfrac{2}{9})+(-6\dfrac{1}{5})$.
答案
5.(1)原式$=-5-7+6+4=-2.$
(2)原式$=23-17+7-16=23+7-17-16=30+(-33)=-3.$
(3)原式$=-2.4-1.6+7.6+9.4=(7.6-1.6)+(9.4-2.4)=6+7=13.$
(4)原式$=-7+4-9+2+5=-5.$
(5)原式$=\dfrac{2}{3}-\dfrac{4}{5}-\dfrac{1}{5}+\dfrac{1}{4}-1=(-1+\dfrac{2}{3})+(-\dfrac{4}{5}-\dfrac{1}{5})+\dfrac{1}{4}=-\dfrac{1}{3}+(-1)+\dfrac{1}{4}=-\dfrac{13}{12}.$
(6)原式$=-4\dfrac{7}{9}+3\dfrac{1}{5}-2\dfrac{2}{9}-6\dfrac{1}{5}=-4\dfrac{7}{9}-2\dfrac{2}{9}+3\dfrac{1}{5}-6\dfrac{1}{5}=-7-3=-10.$
(2)原式$=23-17+7-16=23+7-17-16=30+(-33)=-3.$
(3)原式$=-2.4-1.6+7.6+9.4=(7.6-1.6)+(9.4-2.4)=6+7=13.$
(4)原式$=-7+4-9+2+5=-5.$
(5)原式$=\dfrac{2}{3}-\dfrac{4}{5}-\dfrac{1}{5}+\dfrac{1}{4}-1=(-1+\dfrac{2}{3})+(-\dfrac{4}{5}-\dfrac{1}{5})+\dfrac{1}{4}=-\dfrac{1}{3}+(-1)+\dfrac{1}{4}=-\dfrac{13}{12}.$
(6)原式$=-4\dfrac{7}{9}+3\dfrac{1}{5}-2\dfrac{2}{9}-6\dfrac{1}{5}=-4\dfrac{7}{9}-2\dfrac{2}{9}+3\dfrac{1}{5}-6\dfrac{1}{5}=-7-3=-10.$
