Tính: - 11 12 - - 1
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a.
\(\left(1\frac{1}{4}+\frac{3}{5}\right):\left(-\frac{11}{12}\right)+\left(\frac{3}{8}-1\frac{2}{5}\right):\left(-\frac{11}{12}\right)\)
\(=\left(\frac{5}{4}+\frac{3}{5}+\frac{3}{8}-\frac{7}{5}\right):\left(-\frac{11}{12}\right)\)
\(=\left(\frac{13}{8}-\frac{4}{5}\right):\left(-\frac{11}{12}\right)\)
\(=\frac{33}{40}:\left(-\frac{11}{12}\right)\)
\(=\frac{33}{40}\cdot\left(-\frac{12}{11}\right)\)
\(=\frac{-9}{10}\)
b.
\(\left(\frac{3}{8}-1\frac{2}{5}\right):\left(-\frac{11}{15}\right)+\left(1\frac{1}{4}+\frac{3}{5}\right):\left(-\frac{11}{15}\right)\)
\(=\left(\frac{3}{8}-\frac{7}{5}+\frac{5}{4}+\frac{3}{5}\right):\left(-\frac{11}{15}\right)\)
\(=\left(\frac{13}{8}-\frac{4}{5}\right):\left(-\frac{11}{15}\right)\)
\(=\frac{33}{40}:\left(-\frac{11}{15}\right)\)
\(=\frac{33}{40}\cdot\left(-\frac{15}{11}\right)\)
\(=\frac{-9}{8}\)
\(=\dfrac{11}{12}\left(\dfrac{2}{7}+\dfrac{4}{7}+\dfrac{1}{7}\right)=\dfrac{11}{12}\cdot1=\dfrac{11}{12}\)
\(S=\frac{1}{10.11}+\frac{1}{11.12}+...+\frac{1}{99.100}\)
\(\Rightarrow S=\frac{1}{10}-\frac{1}{11}+\frac{1}{11}-\frac{1}{12}+...+\frac{1}{99}-\frac{1}{100}\)
\(\Rightarrow S=\frac{1}{10}-\frac{1}{100}\)
\(\Rightarrow S=\frac{99}{100}\)
\(S=\frac{1}{10.11}+\frac{1}{11.12}+....+\frac{1}{99.100}\)
\(=\frac{11-10}{10.11}+\frac{12-11}{11.12}+...+\frac{100-99}{99.100}\)
\(=\frac{11}{10.11}-\frac{10}{10.11}+\frac{12}{11.12}-\frac{11}{11.12}+....+\frac{100}{99.100}-\frac{99}{99.100}\)
\(=\frac{1}{10}-\frac{1}{11}+\frac{1}{11}-\frac{1}{12}+....+\frac{1}{99}-\frac{1}{100}\)
\(=\frac{1}{10}-\frac{1}{100}=\frac{9}{100}\)
\(\frac{1}{10.11}+\frac{1}{11.12}+\frac{1}{12.13}+.......+\frac{1}{49.50}\)
\(=\frac{1}{10}-\frac{1}{11}+\frac{1}{11}-\frac{1}{12}+......+\frac{1}{50}\)
\(=\frac{1}{10}-\frac{1}{50}=\frac{2}{25}\)
`#` `\text{dkhanhqlv}`
`a)1/8-1/2`
`=1/8-4/8`
`=-3/8`
`b)-11/12-(-1)`
`=-11/12+1`
`=-11/12+12/12`
`=1/12`
`c)3/5-5/6`
`=18/30-25/30`
`=-7/30`
`d)-1/16-1/15`
`=-15/240-16/240`
`=-31/240`
`e)11/36-(-7/24)`
`=11/36+7/24`
`=22/72+21/72`
`=43/72`
`g)-5/9-(-5/12)`
`=-5/9+5/12`
`=-20/36+15/36`
`=-5/36`
a) \(\dfrac{1}{8}-\dfrac{1}{2}=\dfrac{1}{8}-\dfrac{4}{8}=-\dfrac{3}{8}\)
b) \(-\dfrac{11}{12}-\left(-1\right)=-\dfrac{11}{12}+\dfrac{12}{12}=\dfrac{1}{12}\)
c) \(\dfrac{3}{5}-\dfrac{5}{6}=\dfrac{18}{30}-\dfrac{25}{30}=-\dfrac{7}{30}\)
d) \(-\dfrac{1}{16}-\dfrac{1}{15}=-\dfrac{15}{240}-\dfrac{16}{240}=-\dfrac{31}{240}\)
e) \(\dfrac{11}{36}-\left(-\dfrac{7}{24}\right)=\dfrac{11}{36}+\dfrac{7}{24}=\dfrac{22}{72}+\dfrac{21}{72}=\dfrac{43}{72}\)
g) \(-\dfrac{5}{9}-\left(-\dfrac{5}{12}\right)=-\dfrac{5}{9}+\dfrac{5}{12}=-\dfrac{20}{36}+\dfrac{15}{36}=-\dfrac{5}{36}\)
a)=\(-\dfrac{3}{8}\)
b)=\(\dfrac{13}{12}\)
c)=\(-\dfrac{7}{36}\)
d)=\(-\dfrac{5}{36}\)
\(\dfrac{1}{8}-\dfrac{1}{2}=\dfrac{1-4}{8}=\dfrac{-3}{8}.\\ \dfrac{-11}{12}-\left(-2\right)=\dfrac{-11}{12}+2=\dfrac{13}{12}.\\ \dfrac{-1}{12}-\dfrac{1}{9}=\dfrac{-7}{36}.\\ \dfrac{-5}{9}-\dfrac{-5}{12}=\dfrac{-5}{36}.\)
\(1)\frac{11}{12}-\frac{5}{12}\left(0,8-\frac{1}{10}\right):\left(-\frac{7}{12}\right)\)
\(=\frac{11}{12}-\frac{5}{12}\times\frac{7}{10}:\left(-\frac{7}{12}\right)\)
\(=\frac{11}{12}-\frac{7}{24}:\left(-\frac{7}{12}\right)\)
\(=\frac{11}{12}-\left(-\frac{1}{2}\right)\)
\(=\frac{17}{12}\)