1 13/15×3/4-(11/20+1/4)÷7/5
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18 tháng 6 2023
a: =-1+17/20=-3/20
b: =(28/60-33/60)*(-25/3)
=(-1/12)*(-25/3)=1/12*25/3=25/36
c: \(=\dfrac{1}{3}\cdot\dfrac{1}{3}=\dfrac{1}{9}\)
H
3 tháng 3 2023
`4/7+4`
`=4/7+4/1`
`=4/7+28/7`
`=32/7`
__
`3+6/11`
`=33/11+6/11`
`=39/11`
__
`3-5/7`
`=3/1-5/7`
`=21/7-5/7`
`=16/7`
__
`21/9-2`
`=21/9-18/9`
`=3/9`
`=1/3`
__
`15/24+2`
`=15/24+48/24`
`=63/24`
`=21/16`
__
`63/45-20/25`
`=63/45-4/5`
`=63/45-36/45`
`=27/45`
`=9/15`
__
`3/4-2/8`
`=3/4-1/4`
`=2/4`
__
`6/7-5/8`
`=48/56-35/56`
`=13/56`
__
`37/45-5/9`
`=37/45-25/45`
`=12/45`
`=4/15`
__
`46/39-11/13`
`=46/39-33/39`
`=13/39`
`=1/2`
__
`5/12+3/4+1/3`
`=5/12+9/12+4/12`
`=14/12+4/12`
`=18/12`
`=3/2`
__
`1/2+3/7+11/14`
`=7/14+6/14+11/14`
`=13/14+11/14`
`=24/14`
`=12/7`
__
`7/10-(1/5+1/4)`
`=7/10-(4/20+5/20)`
`=7/10-9/20`
`=14/20-9/20`
`=5/20`
`=1/4`
__
`15/4-2/3-3/4`
`=(15/4-3/4)-2/3`
`=12/4-2/3`
`=3-2/3`
`=9/3-2/3`
`=7/3`
20 tháng 4 2023
= 4/9 : -8 - (-1/4 + 9/20) : 14/5
= 4/9 : -8 - 1/5 : 14/5
= -1/18 - 1/5 : 14/5
= -1/18 - 1/14
= -8/63
TN
22 tháng 7 2016
1)C= 1/5+1/10+1/20+1/40+...+1/1280
\(=\frac{1}{5}\left(1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^8}\right)\)
Đặt cái trong ngoặc là A ta có:\(2A=2+1+...+\frac{1}{2^7}\)
\(2A-A=\left(2+1+...+\frac{1}{2^7}\right)-\left(1+\frac{1}{2}+...+\frac{1}{2^8}\right)\)
\(A=2-\frac{1}{2^8}\).Thay A vào ta được:\(C=\frac{1}{5}\left(2-\frac{1}{2^8}\right)=\frac{1}{5}\cdot\frac{511}{256}=\frac{511}{1280}\)
2)D= 2/1*3+2/3*5+2/5*10+2/7*9+2/9*11+2/11*18+2/13*15
\(=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{13}-\frac{1}{15}\)
\(=1-\frac{1}{15}\)
\(=\frac{14}{15}\)
3)E= 4/3*7+4/7*11+4/11*15+4/15*19+4/19*23+4/23*27
\(=\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+...+\frac{1}{23}-\frac{1}{27}\)
\(=\frac{1}{3}-\frac{1}{27}\)
\(=\frac{8}{27}\)
4)G= 1/2+1/6+1/12+1/20+1/30+1/42+...+1/110
\(=\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{10.11}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{10}-\frac{1}{11}\)
\(=1-\frac{1}{11}\)
\(=\frac{10}{11}\)
5)H= 3/1*2+3/2*3+3/3*4+3/4*5+...+3/9*10
\(=3\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}\right)\)
\(=3\left(1-\frac{1}{10}\right)\)
\(=3\times\frac{9}{10}\)
\(=\frac{27}{10}\).Lần sau bạn đăng ít một thôi nhé
Q
21 tháng 4 2017
\(A=\left(\dfrac{5}{12}.\dfrac{21}{15}\right):\dfrac{1}{4}\)
\(=\dfrac{7}{12}:\dfrac{1}{4}\)
\(=\dfrac{28}{12}=\dfrac{7}{3}\)
\(B=\left(\dfrac{2}{7}:\dfrac{5}{4}\right).\left(\dfrac{5}{8}:2\right)\)
\(=\dfrac{8}{35}.\left(\dfrac{5}{8}:2\right)\)
\(=\dfrac{8}{35}.\dfrac{5}{16}\)
\(=\dfrac{1}{14}\)
\(C=\left(\dfrac{11}{15}.\dfrac{35}{44}\right).\left(\dfrac{1}{7}.\dfrac{4}{13}\right)\)
\(=\dfrac{7}{12}.\left(\dfrac{1}{7}.\dfrac{4}{13}\right)\)
\(=\dfrac{7}{12}.\left(\dfrac{1}{7}.\dfrac{4}{13}\right)\)
\(=\dfrac{7}{12}.\dfrac{4}{91}\)
\(=\dfrac{1}{39}\)
\(D=\left(\dfrac{7}{20}+\dfrac{11}{15}-\dfrac{15}{12}\right):\left(\dfrac{11}{20}-\dfrac{26}{45}\right)\)
\(=\left(\dfrac{13}{12}-\dfrac{15}{12}\right):\left(\dfrac{11}{20}-\dfrac{26}{45}\right)\)
\(=\dfrac{-1}{6}:\left(\dfrac{11}{20}-\dfrac{26}{45}\right)\)
\(=\dfrac{-1}{6}:\dfrac{-1}{36}\)
\(=6\)
\(1\dfrac{13}{15}\times\dfrac{3}{4}-\left(\dfrac{11}{20}+\dfrac{1}{4}\right):\dfrac{7}{5}\)
\(=\dfrac{28}{15}\times\dfrac{3}{4}-\left(\dfrac{11}{20}+\dfrac{5}{20}\right):\dfrac{7}{5}\)
\(=\dfrac{7}{5}\times1-\dfrac{16}{20}:\dfrac{7}{5}\)
\(=\dfrac{7}{5}-\dfrac{16}{20}\times\dfrac{5}{7}\)
\(=\left(\dfrac{7}{5}\times\dfrac{5}{7}\right)-\dfrac{16}{20}\)
\(=\dfrac{1}{1}-\dfrac{16}{20}\)
\(=1-\dfrac{4}{5}\)
\(=\dfrac{1}{5}\)
Sửa lại, xin lỗi bạn, bạn thông cảm giúp mình nhé!
\(1\dfrac{13}{15}\times\dfrac{3}{4}-\left(\dfrac{11}{20}+\dfrac{1}{4}\right):\dfrac{7}{5}\)
\(=\dfrac{28}{15}\times\dfrac{3}{4}-\left(\dfrac{11}{20}+\dfrac{5}{20}\right)\times\dfrac{5}{7}\)
\(=\dfrac{7}{5}\times1-\dfrac{16}{20}\times\dfrac{5}{7}\)
\(=\dfrac{7}{5}-\dfrac{80}{140}\)
\(=\dfrac{7}{5}-\dfrac{4}{7}\)
\(=\dfrac{49}{35}-\dfrac{20}{35}\)
\(=\dfrac{29}{35}\)