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20 tháng 6 2020

\(\left(0,25-30\%.x\right).\frac{1}{3}-\frac{1}{4}=-5\frac{1}{6}\)

\(< =>\left(\frac{1}{4}-\frac{3x}{10}\right).\frac{1}{3}-\frac{1}{4}=-\frac{30}{6}\)

\(< =>\left(\frac{1}{4}-\frac{3x}{10}\right).\frac{1}{3}=-5+\frac{1}{4}=-\frac{19}{4}\)

\(< =>\frac{1}{4}-\frac{3x}{10}=\frac{-19}{4}.\frac{3}{1}=-\frac{57}{4}\)

\(< =>\frac{-3x}{10}=\frac{-57}{4}-\frac{1}{4}=-\frac{58}{4}\)

\(< =>-12x=-580\)

\(< =>12x=580< =>x=\frac{580}{12}=\frac{145}{3}\)

20 tháng 6 2020

\(\left(0,25-30\%x\right).\frac{1}{3}-\frac{1}{4}=-5\frac{1}{6}\)

\(\left(\frac{1}{4}-\frac{3}{10}x\right)\frac{1}{3}-\frac{1}{4}=\frac{-31}{6}\)

\(\frac{1}{4}-\frac{3}{10}x=\left(\frac{-31}{6}+\frac{1}{4}\right)\div\frac{1}{3}\)

\(\frac{1}{4}-\frac{3}{10}x=\frac{-59}{4}\)

\(\frac{3}{10}x=\frac{1}{4}-\frac{-59}{4}\)

\(\frac{3}{10}x=15\Leftrightarrow x=50\)

30 tháng 5 2015

\(-3\frac{3}{5}-30\%x=0,45-1\frac{3}{4}x\)

\(-\frac{18}{5}-\frac{3}{10}x=\frac{9}{20}-\frac{7}{4}x\)

\(-\frac{3}{10}x+\frac{7}{4}x=\frac{18}{5}+\frac{9}{20}=\frac{72}{20}+\frac{9}{20}\)

\(\left(-\frac{3}{10}+\frac{7}{4}\right)x=\frac{81}{20}\)

\(\left(-\frac{6}{20}+\frac{35}{20}\right)x=\frac{81}{20}\)

\(\frac{29}{20}x=\frac{81}{20}\)

\(x=\frac{81}{20}:\frac{29}{20}=\frac{81}{20}\cdot\frac{20}{29}=\frac{81}{29}\)

Vậy \(x=\frac{81}{29}\)

Chúc bạn học tốt!^_^

 

30 tháng 5 2015

sửa lại nè

\(\frac{41}{20}x=-\frac{72}{20}-\frac{9}{20}\)

\(\frac{41}{20}x=-\frac{81}{20}\)

\(x=\frac{-81}{20}:\frac{41}{20}\)

\(x=-\frac{81}{41}\)

25 tháng 3 2018

a)\(x-\frac{1}{4}=\frac{5}{8}\)

\(x=\frac{5}{8}+\frac{1}{4}\)

\(x=\frac{7}{8}\)

b)\(\frac{x}{12}=\frac{-1}{24}-\frac{1}{8}\)

\(\frac{x}{12}=\frac{-1}{24}+\frac{-1}{8}\)

\(\frac{x}{12}=\frac{-1}{6}\)

\(x=\frac{-1}{6}\times12\)

\(x=-2\)

25 tháng 3 2018

a)x-1/4=5/8

=>x=5/8+1/4

x=7/8

b) x/12=-1/24-1/8

=>x/12=-1/6

=>x=-2

c).......... Tự làm

24 tháng 5 2017

\(x+x:0,25+x:0,5+x:0,125=0,45\)

\(\Rightarrow x+x:\dfrac{1}{4}+x:\dfrac{1}{2}+x:\dfrac{1}{8}=0,45\)

\(\Rightarrow x+4x+2x+8x=0,45\)

\(\Rightarrow15x=0,45\)

\(\Rightarrow x=0,3\)

Vậy x = 0,3

24 tháng 5 2017

Cảm ơn bạn nhiều nha

2 tháng 9 2016

a, (10/3:x).(-5/4)=-10/3

10/3:x=-10/3:(-5/4)

10/3:x=8/3

x=10/3:8/3

x=5/4

b,(-6/5+x):(-18/5)=-1/4

-6/5+x=-1/4.(-18/5)

-6/5+x=9/10

x=9/10-(-6/5)=9/10+6/5

x=21/10

c,-22/15.x+1/3=-2/5

-22/15.x=-2/5-1/3=-11/15

x=-11/15:(-22/15)

x=11/21

d,(0,25-30%x).1/3=-31/6+1/4=-59/12

1/4-3/10x=-59/12:1/3=-59/4

3/10x=1/4-(-59/4)=1/4+59/4=15

x=15:3/10

x=50

e,(0,5x-3/7):1/2=8/7

1/2x=8/7.1/2=4/7

x=4/7:1/2

x=8/7

a) Ta có: \(\left(x-2\right)^3+\frac{8}{27}=0\)

\(\Leftrightarrow\left(x-2\right)^3=\frac{-8}{27}\)

\(\Leftrightarrow\left(x-2\right)^3=\left(-\frac{2}{3}\right)^3\)

\(\Leftrightarrow x-2=\frac{-2}{3}\)

hay \(x=\frac{-2}{3}+2=\frac{4}{3}\)

Vậy: \(x=\frac{4}{3}\)

b) Ta có: \(4\frac{1}{3}:\frac{x}{4}=6:0,3\)

\(\Leftrightarrow\frac{13}{3}\cdot\frac{4}{x}=20\)

\(\Leftrightarrow\frac{4}{x}=20:\frac{13}{3}=20\cdot\frac{3}{13}=\frac{60}{13}\)

hay \(x=\frac{13\cdot4}{60}=\frac{13}{15}\)

Vậy: \(x=\frac{13}{15}\)

c) Ta có: \(\left(0,25-30\%x\right)\cdot\frac{1}{3}-\frac{1}{4}=5\frac{1}{6}\)

\(\Leftrightarrow\left(\frac{1}{4}-\frac{3x}{10}\right)\cdot\frac{1}{3}=\frac{31}{6}+\frac{1}{4}=\frac{65}{12}\)

\(\Leftrightarrow\frac{1}{4}-\frac{3x}{10}=\frac{65}{12}:\frac{1}{3}=\frac{65}{12}\cdot3=\frac{65}{4}\)

\(\Leftrightarrow\frac{3x}{10}=\frac{1}{4}-\frac{65}{4}=-16\)

\(\Leftrightarrow3x=-160\)

hay \(x=\frac{-160}{3}\)

Vậy: \(x=\frac{-160}{3}\)

d) Ta có: \(\frac{x-2}{-\frac{2}{9}}=\frac{-2}{x-2}\)

\(\Leftrightarrow\left(x-2\right)^2=-2\cdot\left(-\frac{2}{9}\right)=\frac{4}{9}\)

\(\Leftrightarrow\left[{}\begin{matrix}x-2=\frac{2}{3}\\x-2=-\frac{2}{3}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{2}{3}+2\\x=\frac{-2}{3}+2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{8}{3}\\x=\frac{4}{3}\end{matrix}\right.\)

Vậy: \(x\in\left\{\frac{8}{3};\frac{4}{3}\right\}\)

30 tháng 3 2020

a/ (x - 2)3 + \(\frac{8}{27}\) = 0

=> (x - 2)3 = 0 - \(\frac{8}{27}\) = \(\frac{-8}{27}\)

=> x - 2 = \(-\frac{2}{3}\)

=> x = \(-\frac{2}{3}+2=\frac{4}{3}\)

b/ \(4\frac{1}{3}:\frac{x}{4}=6:0,3\)

=> \(4\frac{1}{3}:\frac{x}{4}=6:\frac{3}{10}=6.\frac{10}{3}=20\)

=> \(\frac{x}{4}=4\frac{1}{3}:20=\frac{13}{3}.\frac{1}{20}=\frac{13}{60}\)

=> \(x=\frac{13}{60}.4=\frac{13}{15}\)

c/ \(\left(0,25-30\%x\right).\frac{1}{3}-\frac{1}{4}=5\frac{1}{6}\)

=> \(\left(0,25-30\%x\right).\frac{1}{3}=5\frac{1}{6}+\frac{1}{4}=\frac{65}{12}\)

=> \(0,25-\frac{30}{100}x=\frac{65}{12}:\frac{1}{3}=\frac{65}{12}.3=\frac{65}{4}\)

=> \(\frac{3}{10}x=0,25-\frac{65}{4}=\frac{1}{4}-\frac{65}{4}=-\frac{64}{4}=-16\)

=> \(x=-16:\frac{3}{10}=-16.\frac{10}{3}=-\frac{160}{3}\)

a,  0,25 - x = -0,75

               x = 0,25 - -0,75

               x = 1

 b,x:(-3)= -\(\frac{2}{3}\) 

          x = -\(\frac{2}{3}\) >< -3

         x = -2

c,(1,1.x-9).\(\frac{2}{5}\)=80%

1,1 >< x -9 = \(\frac{80}{100}\) : \(\frac{2}{5}\)

1,1 >< x -9 = 2

1,1 >< x     = 2 + 9

1,1 >< x     = 11

          x      =11 : 1,1

         x = 10

d,2.x-30%.x=-1,7

   x >< (2-0,3)=1,7

   x >< 0,7     = 1,7

           x        = 1,7 : 0,7 

          x        = 2.42857142857

30 tháng 4 2019

a)0,25-x=-0,75

          x=

9-0,75-0,25

         x=-1

b)x:(-3)=-2/3

  x        =(-2/3).(-3)

 x         =6/3

c)(1,1.x-9).2/5=80%

   (1,1.x-9).2/5=80/100=4/5

    1,1.x-9       =4/5:2/5

     1,1.x-9      =2/1

      1,1.x        =2/1+9

        1,1.x      =11/1

          x          =11/1:11/10

           x         =10/1=10

mình sẽ làm câu d vào câu trả lời thứ 2