Bài tập: Nhân, Chia số hữu tỉ

−2516=−512.154

−2516=−45:64125.

−2819.−3814=(−28).(−38)19.14=2.2=4

−−2116.−247=21.(−24)16.7=3.(−3)2=−92=−412

−127.1,25=−127.125100=−127.54=−12.57.4=−3.57=−157=−217

−45⋅3216=−45.5016=−4.505.16=−104=−52=−212

12.−232=12.49=12.49=4.43=163=513

(−2)⋅−3821⋅−74⋅−38=(−2).(−38).(−7).(−3)21.4.8=2.38.7.321.4.8=198=238

223⋅25⋅38⋅10⋅1992=83.25.38.10.1992=8.2.3.10.193.5.8.92=1923

P=−813⋅169⋅−138⋅−18=(−8).16.(−13).(−18)13.9.8=−32

−43:139=−43.913=−4.93.13=−1213

−925:6=−925.16=(−9).125.6=−350

1112:2116=1112:3316=1112.1633=11.1612.33=49

3,5:−32=3510:−32=72.−23=7.(−2)2.3=−73=−213

−132:(−4):213=−132:(−4):73=−132.−14.37=1.1.332.4.7=3896

−34⋅12−5:−2516=−34⋅12−5⋅−1625=95.−1625=−144125

−57⋅493:−76=−57⋅493⋅−67=10

1,75:−12⋅−23=74.−112.−23=772

−9⋅23⋅54:−7=−9.56.−17=1514

0,8:−245⋅−522=45:−145.254=45.−514.254=−2514

21−334:38−16=21−154:524=21−18=3

723⋅−86−4518=723.−236=−76

0,75−14:−56=34−14.−65=12.−65=−35

54−54:38−16+1112=54−54:524+1112=54−6+1112=−194+1112=−236

1,25⋅5−43⋅−711=54.113.−711=−3512

−9⋅23−54:−7=−9.−712.−17=−34

134−0,25.213=74−14.73=32.73=72

234−0,25.213=114−14.73=52.73=356

73−52:34+32=−16:94=−16.49=−227

925−2.18:345+0,2=925−36:195+15=−89125:4=−891100

0,84−0,64+49+41379+713−0,2+0,55=0,2+49+41379+713+0,35=420+49+41379+713+720=4120+19+1137120+19+113=47

 38.1913−38.3313 =38.1913−3313 =38.−14=−214

12,5.−57+1,5.−57=−57.12,5+1,5=−57.14=−10

35:−1115−16+35:−13−1115=35:−1615−16+35:−13−1615=35:−3730+35:-75=35.−3037+35.-57=35.-3037+-57=35.-395259=−237259

−34+25:37+35+−14:37=−34+25.73+35+−14.73=73.−34+25+35+−14=73.-34+-14+25+35=73.−1+1=0

A=0,25×7+0,2520,4×52−25A=74+116.25.25−25A=2916.485A=875=1725

B=289−3178⋅8917+3334B=4178−3178.8917+3334B=1178.8917+3334B=134+3334=1

Vậy A>B

A= 1−12.1−13.1−14...1−119.1−120A=12.23.34....1819.1920A=120>121

Vậy A>121

B=12.23.34.....99100= 1100<1

Vậy B < 1

52x=−310−−45=>52x=12=>x=12:52=>x=15

58:x=112−43⇒58:x=−54=>x=58:−54=-12

Từ đề bài ta có x-13=0 hoặc x+25=0. Tìm được x=13hoặc x=-25

x = 3/4 hoặc x = 2/5

 A=1−11.2+1−12.3+...+1−12015.2016       =1+1+1+...1−11.2+12.3+...+12015.2016       =2015−1−12+12−13+13−14+...+12015−12016       =2015−1−12016       =2015−1+12016       =2014+12016       =40602252016

B=31.4+54.9+79.16+916.25+1125.36       =1−14+14−19+19−116+116−125+125−136       =1−136       =3536

C=31.4+34.7+...+3100.103       =1−14+14−17+...+1100−1103       =1−1103       =102103

 D=31.4+64.10+910.19+1219.31+1531.46+1846.64        =4−11.4+10−44.10+19−1010.19+31−1919.31+46−3131.46+64−4646.64        =1−14+14−110+110−119+119−131+131−146+146−164        =1−164        =6364

Ta có:

11.2+13.4+15.6+...+149.50

=1−12+13−14+15−16+⋯⋯+149−150=1+13+15+⋯⋯+149−12+14+16+⋯⋯+150=1+12+13+14+15+⋯⋯+150−2.12+14+16+⋯⋯+150=1+12+13+14+15+⋯⋯+150−1+12+13+⋯⋯+125=126+127+128+...+150     (dpcm)