【例题选讲】
例1解:(1)(+2/3)+(-3/4)
=-(3/4-2/3)
=-1/12;
(2)[-5+(1/4)]+(-3.5)
=-[5(1/4)+3.5]
=-8(3/4);
(3)(-16)+16=0;
(4)(8)+0=-8
例2解:原式=3(1/4)+3(3/5)-5(3/4)+8(2/5)
=[3(1/4)-5(3/4)]+[3(3/5)+8(2/5)]
=-2(1/2)+12=9(1/2).
例3解:(1)(-8)×9×(-1.25)×(-1/9)
=[(-8)×(-1.25)] ×[9×(-1/9)]
=10×(-1)=-10.
(2)[1(1/4)-5/6+1/2)×(-12)
=1(1/4)×(-12)+(-5/6)×(-12)+1/2×(-12)
=-15+10+(-6)=-11
(3)-99(71/22)×36
=-[99(71/72)x36]-[(100-1/72)×36]
=-[100×36-1/72×36]
=-[3600-1/2]
=-3599(1/2).
【课后练习】
1 |
B |
5 |
D |
2 |
B |
6 |
D |
3 |
C |
7 |
B |
4 |
D |
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8、(1)-5
(2)0
(3)-107
(4)71
(5)-200
9、(1)出租车离公园8公里,在公园的东方8公里处
(2)这辆出租车这天下午耗油6.4升
10、(1)π-3.14
(2)0.9
11、(1)-48
(2)-576