Tính
\(\dfrac{ }{ }\)a, -4/7-5/13.-39/25+-1/42:(-5/6)
b, 2/9.[-4/45:(1/5-2/15)+1 2/3]-5/27
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\(a.\dfrac{-4}{7}-\dfrac{5}{13}\times\dfrac{-39}{25}+\dfrac{-1}{42}:\dfrac{-5}{6}\)
\(=\dfrac{-4}{7}+\dfrac{3}{5}+\dfrac{1}{35}\) \(=\dfrac{1}{35}+\dfrac{1}{35}=\dfrac{2}{35}\)
\(b.\dfrac{2}{9}\times\left[\dfrac{4}{5}:\left(\dfrac{1}{5}-\dfrac{2}{15}\right)+1\dfrac{2}{3}\right]-\dfrac{-5}{27}\)
\(=\dfrac{2}{9}\times\left[\dfrac{4}{5}:\dfrac{1}{15}+\dfrac{5}{3}\right]-\dfrac{-5}{27}\)
\(=\dfrac{2}{9}\times\left(12+\dfrac{5}{3}\right)-\dfrac{-5}{27}\)
\(=\dfrac{2}{9}\times\dfrac{41}{3}-\dfrac{-5}{27}=\dfrac{82}{27}-\dfrac{-5}{27}=\dfrac{29}{9}\)
`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`
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`46/39-11/13`
`=46/39-33/39`
`=13/39`
`=1/2`
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`5/12+3/4+1/3`
`=5/12+9/12+4/12`
`=14/12+4/12`
`=18/12`
`=3/2`
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`1/2+3/7+11/14`
`=7/14+6/14+11/14`
`=13/14+11/14`
`=24/14`
`=12/7`
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`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`
câu 1)
\(\dfrac{-12}{18}+\left(\dfrac{-21}{35}\right)=\dfrac{-19}{15}\)
câu 2)
\(-\dfrac{3}{21}+\dfrac{6}{42}=0\)
câu 3)
\(-\dfrac{18}{24}+\dfrac{15}{21}=-\dfrac{1}{28}\)
câu 4)
\(\dfrac{1}{6}+\dfrac{2}{5}=\dfrac{17}{30}\)
câu 5)
\(\dfrac{3}{5}+\left(-\dfrac{7}{4}\right)=-\dfrac{23}{20}\)
câu 6)
\(\left(-2\right)+\left(\dfrac{-5}{8}\right)=\dfrac{-21}{8}\)
câu 7)
\(\dfrac{1}{-8}+\left(-\dfrac{5}{9}\right)=-\dfrac{49}{72}\)
câu 8)
\(\dfrac{4}{13}+\dfrac{12}{39}=\dfrac{8}{13}\)
câu 9)
\(\dfrac{1}{21}+\dfrac{1}{28}=\dfrac{1}{12}\)
câu 10)
\(-\dfrac{3}{29}+\dfrac{16}{58}=\dfrac{5}{29}\)
câu 11)
\(\dfrac{8}{40}+\left(-\dfrac{36}{45}\right)=-\dfrac{3}{5}\)
câu 12)
\(-\dfrac{8}{18}+\left(-\dfrac{15}{27}\right)=-1\)
câu 13)
\(\dfrac{13}{30}+\left(-\dfrac{1}{5}\right)=\dfrac{7}{30}\)
câu 14)
\(\dfrac{2}{21}+\dfrac{1}{28}=\dfrac{11}{84}\)
câu 15)
\(5+\left(-\dfrac{3}{4}\right)=\dfrac{17}{4}\)
câu 16)
\(\dfrac{18}{24}+\dfrac{45}{-10}=-\dfrac{15}{4}\)
1: =-2/9(15/17+2/17)=-2/9
2: \(=\dfrac{-6}{3}+\dfrac{-21}{90}\)
=-2-7/30=-67/30
3: \(=\dfrac{3}{4}\cdot\dfrac{7}{5}+\dfrac{9}{7}\cdot\dfrac{3}{2}\)
=21/20+27/14=417/140
4: =-25/13(5/19+14/19)=-25/13
5: =-7/5-45/21=-7/5-15/7=-124/35
1: =-2/9(15/17+2/17)=-2/9
2: =−63+−2190=−63+−2190
=-2-7/30=-67/30
3: =34⋅75+97⋅32=34⋅75+97⋅32
=21/20+27/14=417/140
4: =-25/13(5/19+14/19)=-25/13
5: =-7/5-45/21=-7/5-15/7=-124/35
a) \(-\frac{4}{7}+\frac{\left(-5\right).\left(-39\right)}{13.25}+\frac{\left(-1\right).6}{42.\left(-5\right)}=-\frac{4}{7}+\frac{\left(-1\right).3}{1.5}+\frac{\left(-1\right).1}{7.\left(-5\right)}=-\frac{4}{7}+\frac{3}{5}+\frac{1}{35}\)
\(=-\frac{20}{35}+\frac{21}{35}+\frac{1}{35}=\frac{2}{35}\)
b) \(=\frac{2}{9}.\left[-\frac{4}{45}:\left(\frac{3}{15}-\frac{2}{15}\right)+1\frac{2}{3}\right]+\frac{5}{27}=\frac{2}{9}.\left[-\frac{4}{45}:\frac{1}{15}+1\frac{2}{3}\right]+\frac{5}{27}\)
\(=\frac{2}{9}.\left[\frac{\left(-4\right).15}{45.1}+1\frac{2}{3}\right]+\frac{5}{27}==\frac{2}{9}.\left[\frac{\left(-4\right).1}{3.1}+1\frac{2}{3}\right]+\frac{5}{27}\)
\(==\frac{2}{9}.\left[-\frac{4}{3}+\frac{5}{3}\right]+\frac{5}{27}=\frac{2.1}{9.3}+\frac{5}{27}=\frac{2}{27}+\frac{5}{27}=\frac{7}{27}\)
\(a,=\dfrac{3^6\cdot5^4\cdot9^4-5^{13}\cdot3^{13}\cdot5^{-9}}{3^{12}\cdot5^6+9^6\cdot5^6}=\dfrac{3^{14}\cdot5^4-5^4\cdot3^{13}}{3^{12}\cdot5^6+3^{12}\cdot5^6}\\ =\dfrac{3^{13}\cdot5^4\cdot2}{2\cdot3^{12}\cdot5^6}=\dfrac{3}{5^2}=\dfrac{3}{25}\)
\(b,=\dfrac{\left(\dfrac{2}{5}\cdot5\right)^7+\left(\dfrac{9}{4}\cdot\dfrac{16}{3}\right)^3}{2^7\cdot5^2+2^9}=\dfrac{2^7+12^3}{2^7\left(5^2+2^2\right)}=\dfrac{2^7+4^3\cdot3^3}{2^7\cdot29}=\dfrac{2^6\left(2+3^3\right)}{2^7\cdot29}=\dfrac{1}{2}\)
\(a,x\left(-\frac{3}{7}\right)=\frac{5}{21}\)
\(\Rightarrow x=\frac{5}{21}:\left(-\frac{3}{7}\right)\)
\(\Rightarrow x=-\frac{5}{9}\)
\(b,x:\left(-\frac{2}{5}\right)=-\frac{15}{16}\)
\(\Rightarrow x=-\frac{15}{16}.\left(-\frac{2}{5}\right)\)
\(\Rightarrow x=\frac{3}{8}\)
\(c,-\frac{4}{7}:x=-\frac{2}{5}\)
\(\Rightarrow x=-\frac{4}{7}:\left(-\frac{2}{5}\right)\)
\(\Rightarrow x=\frac{10}{7}\)
\(d,\frac{2}{3}x+\frac{5}{7}=\frac{3}{10}\)
\(\frac{\Rightarrow2}{3}x=\frac{3}{10}-\frac{5}{7}\)
\(\Rightarrow\frac{2}{3}x=-\frac{29}{70}\)
\(\Rightarrow x=-\frac{29}{70}:\frac{2}{3}\)
\(\Rightarrow x=-\frac{87}{140}\)
a, \(x.\left(-\frac{3}{7}\right)=\frac{5}{21}\)
\(\Rightarrow x=\frac{5}{21}:\left(-\frac{3}{7}\right)\)
\(\Rightarrow x=-\frac{5}{9}\)
b, \(x:\left(-\frac{2}{5}\right)=\left(-\frac{15}{16}\right)\)
\(\Rightarrow x=\left(-\frac{15}{16}\right).\left(-\frac{2}{5}\right)\)
\(\Rightarrow x=\frac{5}{8}\)
c, \(\left(-\frac{4}{7}\right):x=-\frac{2}{5}\)
\(x=\left(-\frac{4}{7}\right):\left(-\frac{2}{5}\right)\)
\(\Rightarrow x=\frac{10}{7}\)
d, \(\frac{2}{3}x+\frac{5}{7}=\frac{3}{10}\)
\(\Rightarrow\frac{2}{3}x=\frac{3}{10}-\frac{5}{7}\)
\(\Rightarrow\frac{2}{3}x=-\frac{29}{70}\)
\(\Rightarrow x=-\frac{29}{70}:\frac{2}{3}\)
\(\Rightarrow x=-\frac{87}{140}\)
e, \(\frac{3}{4}x-\frac{1}{2}=\frac{3}{7}\)
\(\Rightarrow\frac{3}{4}x=\frac{3}{7}+\frac{1}{2}\)
\(\Rightarrow\frac{3}{4}x=\frac{13}{14}\)
\(\Rightarrow x=\frac{13}{14}:\frac{3}{4}\)
\(\Rightarrow x=\frac{26}{21}\)
f, \(\frac{1}{2}x+\frac{3}{5}x=-\frac{33}{25}\)
\(\Rightarrow x\left(\frac{1}{2}+\frac{3}{5}\right)=-\frac{33}{25}\)
\(\Rightarrow\frac{11}{10}x=-\frac{33}{25}\)
\(\Rightarrow x=-\frac{33}{25}:\frac{11}{10}\)
\(\Rightarrow x=-\frac{6}{5}\)
g, \(\left(\frac{2}{3}x-\frac{4}{9}\right)\left(\frac{1}{2}+\left(-\frac{3}{7}\right):x\right)=0\)
\(\orbr{\begin{cases}\frac{2}{3}x-\frac{4}{9}=0\\\frac{1}{2}+-\frac{3}{7}:x=0\end{cases}\Rightarrow\orbr{\begin{cases}\frac{2}{3}x=\frac{4}{9}\\-\frac{3}{7}:x=-\frac{1}{2}\end{cases}\Rightarrow}\orbr{\begin{cases}x=\frac{4}{9}:\frac{2}{3}\\x=-\frac{3}{7}:-\frac{1}{2}\end{cases}\Rightarrow}\orbr{\begin{cases}x=\frac{2}{3}\\x=\frac{6}{7}\end{cases}}}\)
h, \(-\frac{4}{7}-\frac{5}{13}.-\frac{39}{25}+-\frac{1}{42}:-\frac{5}{6}=-\frac{4}{7}+\frac{3}{5}+\frac{1}{35}\)
\(=\frac{-20+21+1}{35}=\frac{2}{35}\)
i, \(\frac{2}{9}\left[-\frac{4}{45}:\left(\frac{1}{5}-\frac{2}{15}\right)+1\frac{2}{3}\right]--\frac{5}{27}=\frac{2}{9}\left(-\frac{4}{45}:\frac{3-2}{15}+\frac{5}{3}\right)+\frac{5}{27}\)
\(=\frac{2}{9}\left(-\frac{4}{45}.15+\frac{5}{3}\right)+\frac{5}{27}=\frac{2}{9}\left(-\frac{4}{3}+\frac{5}{3}\right)+\frac{5}{27}\)
\(=\frac{2}{9}.\frac{1}{3}+\frac{5}{27}=\frac{2}{27}+\frac{5}{27}=\frac{7}{27}\)
a: \(-\dfrac{4}{7}-\dfrac{5}{13}\cdot\dfrac{-39}{25}+\dfrac{-1}{42}:\dfrac{-5}{6}\)
\(=\dfrac{-4}{7}+\dfrac{3}{5}+\dfrac{1}{35}\)
\(=\dfrac{-20}{35}+\dfrac{21}{35}+\dfrac{1}{35}\)
\(=\dfrac{2}{35}\)