\(\frac{4}{2\cdot7}=\frac{4\cdot5}{2\cdot7\cdot5}=\frac{20}{70}\)

\(\frac{11}{7\cdot5}=\frac{11\cdot2}{7\cdot5\cdot2}=\frac{22}{70}\)

\(\frac{9}{2\cdot5}=\frac{9\cdot7}{2\cdot5\cdot7}=\frac{63}{70}\)

=))

\(\dfrac{x+5}{2015}+\dfrac{x+6}{2014}+\dfrac{x+7}{2013}+\dfrac{x+8}{2012}=-4\\ \Leftrightarrow\left(\dfrac{x+5}{2015}+1\right)+\left(\dfrac{x+6}{2014}+1\right)+\left(\dfrac{x+7}{2013}+1\right)+\left(\dfrac{x+8}{2012}+1\right)=0\\ \Leftrightarrow\dfrac{x+2020}{2015}+\dfrac{x+2020}{2014}+\dfrac{x+2020}{2013}+\dfrac{x+2020}{2012}=0\\ \Leftrightarrow\left(x+2020\right)\left(\dfrac{1}{2015}+\dfrac{1}{2014}+\dfrac{1}{2013}+\dfrac{1}{2012}\right)=0\\ \Leftrightarrow x+2020=0\\ \Leftrightarrow x=-2020\)

Vậy x = -2020 là nghiệm của pt.

\(\dfrac{x+5}{2015}+\dfrac{x+6}{2014}+\dfrac{x+7}{2013}+\dfrac{x+8}{2012}=-4\)

\(\Leftrightarrow x+2020=0\)

hay x=-2020

khó quá nhiw

= 51/20

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= 3/14

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= 4/7 - 2/7 

= 2/7

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= 17/45

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= 2/3 

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= 2 x 1/4 

= 1/2

a: \(x+\dfrac{3}{9}=\dfrac{7}{6}\cdot\dfrac{2}{3}\)

=>\(x+\dfrac{1}{3}=\dfrac{14}{18}=\dfrac{7}{9}\)

=>\(x=\dfrac{7}{9}-\dfrac{1}{3}=\dfrac{7}{9}-\dfrac{3}{9}=\dfrac{4}{9}\)

b: \(x-\dfrac{2}{3}=\dfrac{1}{8}:\dfrac{5}{4}\)

=>\(x-\dfrac{2}{3}=\dfrac{1}{8}\cdot\dfrac{4}{5}=\dfrac{1}{10}\)

=>\(x=\dfrac{1}{10}+\dfrac{2}{3}=\dfrac{3+20}{30}=\dfrac{23}{30}\)

TThế giới oi oi oi 

a; \(\dfrac{2}{3}\)\(x\) - \(\dfrac{3}{2}\)\(x\) = \(\dfrac{5}{12}\)

    (\(\dfrac{2}{3}\) - \(\dfrac{3}{2}\))\(x\) = \(\dfrac{5}{12}\)

     - \(\dfrac{5}{6}\)\(x\) = \(\dfrac{5}{12}\)

     \(x\)   = \(\dfrac{5}{12}\) : (- \(\dfrac{5}{6}\))

     \(x=\) - \(\dfrac{1}{2}\)

Vậy \(x=-\dfrac{1}{2}\) 

b; \(\dfrac{2}{5}\) + \(\dfrac{3}{5}\).(3\(x\) - 3,7) = \(\dfrac{-53}{10}\)

           \(\dfrac{3}{5}\).(3\(x\) - 3,7) = \(\dfrac{-53}{10}\) - \(\dfrac{2}{5}\)

          \(\dfrac{3}{5}\).(3\(x\) - 3,7) = - \(\dfrac{57}{10}\)

         3\(x\) - 3,7 = - \(\dfrac{57}{10}\) : \(\dfrac{3}{5}\)

         3\(x\)   - 3,7 = - \(\dfrac{19}{2}\)

         3\(x\)         = - \(\dfrac{19}{2}\) + 3,7

          3\(x\)        = - \(\dfrac{29}{5}\)

           \(x\)         = - \(\dfrac{29}{5}\) : 3

           \(x\)        = - \(\dfrac{29}{15}\)

Vậy \(x\) \(\in\) - \(\dfrac{29}{15}\) 

c; \(\dfrac{7}{9}\) : (2 + \(\dfrac{3}{4}\)\(x\)) + \(\dfrac{5}{9}\) = \(\dfrac{23}{27}\)

    \(\dfrac{7}{9}\): (2 + \(\dfrac{3}{4}\)\(x\)) = \(\dfrac{23}{27}\) - \(\dfrac{5}{9}\)

     \(\dfrac{7}{9}\):(2 + \(\dfrac{3}{4}\)\(x\)) = \(\dfrac{8}{27}\)

      2 + \(\dfrac{3}{4}\)\(x\) = \(\dfrac{7}{9}\) : \(\dfrac{8}{27}\)

      2 + \(\dfrac{3}{4}\)\(x\) =  \(\dfrac{21}{8}\)

             \(\dfrac{3}{4}x\) = \(\dfrac{21}{8}\) - 2

             \(\dfrac{3}{4}\)\(x\) =  \(\dfrac{5}{8}\)

               \(x\) = \(\dfrac{5}{8}\) : \(\dfrac{3}{4}\)

              \(x\) =  \(\dfrac{5}{6}\)

Vậy \(x=\dfrac{5}{6}\)

a)x*4/5:2=6/7               b)6/5:x:5/4=10/15

x*4/5=6/7 x 2                6/5:x=10/15 x 5/4

x*4/5=12/7                     6/5:x=5/6

x=12/7:4/5                       x=6/5:5/6

x=15/7                            x=36/25

a) x * 4/5 : 2 = 6/7

x * 4/5 = 6/7 *2

x *4/5        = 12/7

x                = 12/7 : 4/5

x               = 15/7

    Vậy x = 15/7

b) 6/5 : x : 5/4 = 10/15

6/5 : x              = 10/15 * 5/4

6/5 :x               =5/6

        x              = 6/5  : 5/6

        x               = 36/25

         Vậy x = 36/25

1) = \(\frac{3}{5}\)

2) =\(\frac{6}{7}\)

3)\(\frac{9}{13}\)

4)\(\frac{4}{13}\)