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19 tháng 1 2017

dấu / / là giá trị tuyệt đối

a) / x + 3 / = 15

=> x + 3 = 15 hay x + 3 = -15

TH1 : x + 3 = 15

           x =15 - 3

           x = 12

TH2 :  x + 3 = -5

             x = -5 - 3

             x = -8

VẬy : x thuộc { 12;-8 }

b ) /x-7/ + 13 = 25

      / x - 7 / = 25 - 13

      / x - 7 / = 12

   => x - 7 = 12 hay x -  7 = -12

TH1 : x - 7 = 12

         x = 12 + 7

         x =19

TH2: x - 7 = -12

          x = -12 + 7

          x = -5

Vậy : x thuộc { 19; -5 }

c) 3 ( x + 3 )2 = 27

  ( x + 3 )2 = 27 : 3

  ( x + 3 ) 2 = 9

x + 3 = 3 hay x + 3 = -3 ( lũy thừa bậc chẵn )

Th1 : x + 3 = 3

         x = 3 -3 

         x = 0

TH2 : x + 3 = -3

           x = -3-3

       x = -6

Vậy : x thuộc { 0 ; -6 }

d) 20 - 2 ( 1-x )3 = 4

 2 ( 1 - x )3 = 20 - 4

 2 ( 1 - x )3 = 16

( 1 - x )3 = 16 : 2

 ( 1 -x )3 = 8

 ( 1 - x )3 = 2

=> 1 - x = 2

   x = 1 - 2

   x = -1

VẬy : x = -1

29 tháng 3 2022

a) \(\dfrac{2}{5}\cdot x=\dfrac{1}{2}+\dfrac{6}{8}\)

    \(\dfrac{2}{5}\cdot x=\dfrac{5}{4}\)

          \(x=\dfrac{5}{4}\div\dfrac{2}{5}\)

          \(x=\dfrac{25}{8}\)

b) \(\dfrac{20}{7}-x=\dfrac{19}{7}\div\dfrac{3}{2}\)

    \(\dfrac{20}{7}-x=\dfrac{19}{7}\cdot\dfrac{2}{3}\)

    \(\dfrac{20}{7}-x=\dfrac{38}{21}\)

             \(x=\dfrac{20}{7}-\dfrac{28}{21}\)

             \(x=\dfrac{22}{21}\)

29 tháng 3 2022

a) x=25/8

b)=22/21

19 tháng 6 2023

\(\left(x+2\right)-2=0\)

\(\Rightarrow x+2-2=0\)

\(\Rightarrow x=0\)

\(\left(x+3\right)+1=7\)

\(\Rightarrow x+3+1=7\)

\(\Rightarrow x+4=7\)

\(\Rightarrow x=3\)

\(\left(3x-4\right)+4=12\)
\(\Rightarrow3x-4+4=12\)

\(\Rightarrow3x=12\)

\(\Rightarrow x=4\)

\(\left(5x+4\right)-1=13\)

\(\Rightarrow5x+4-1=13\)

\(\Rightarrow5x+3=13\)

\(\Rightarrow5x=10\)

\(\Rightarrow x=2\)

\(\left(4x-8\right)-3=5\)

\(\Rightarrow4x-8-3=5\)

\(\Rightarrow4x-11=5\)

\(\Rightarrow4x=16\)

\(\Rightarrow x=4\)

\(8-\left(2x+4\right)=2\)

\(\Rightarrow8-2x-4=2\)

\(\Rightarrow4-2x=2\)

\(\Rightarrow2x=2\)

\(\Rightarrow x=1\)

\(7+\left(5x+2\right)=14\)

\(\Rightarrow7+5x+2=14\)

\(\Rightarrow9+5x=14\)

\(\Rightarrow5x=5\)

\(\Rightarrow x=1\)

\(5-\left(3x-11\right)=1\)

\(\Rightarrow5-3x+11=1\)

\(\Rightarrow16-3x=1\)

\(\Rightarrow3x=15\)

\(\Rightarrow x=5\)

30 tháng 11 2023

1) -x - 3 = 7

-x = 7 + 3

-x = 10

x = -10

2) x + 5 = -10

x = -10 - 5

x = -15

3) 2x - 7 = 713

2x = 713 + 7

2x = 720

x = 720 : 2

x = 360

4) -129 - (35 - x) = 55

35 - x = -129 - 55

35 - x = -184

x = 35 - (-184)

x = 219

5) 103 - x = 16 - (13 - 8)

103 - x = 16 - 5

103 - x = 11

x = 103 - 11

x = 192

16 tháng 8 2023

a) \(\dfrac{13}{20}+\dfrac{3}{5}+x=\dfrac{5}{6}\)

\(\Rightarrow\dfrac{5}{4}+x=\dfrac{5}{6}\)

\(\Rightarrow x=\dfrac{5}{6}-\dfrac{5}{4}\)

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

b) \(x+\dfrac{1}{3}=\dfrac{2}{5}-\dfrac{-1}{3}\)

\(\Rightarrow x+\dfrac{1}{3}=\dfrac{11}{15}\)

\(\Rightarrow x=\dfrac{11}{15}-\dfrac{1}{3}\)

\(\Rightarrow x=\dfrac{2}{5}\)

c)\(\dfrac{-5}{8}-x=\dfrac{-3}{20}-\dfrac{-1}{6}\)

\(\dfrac{-5}{8}-x=\dfrac{1}{60}\)

\(\Rightarrow x=\dfrac{-5}{8}-\dfrac{1}{60}\)

\(\Rightarrow x=\dfrac{-77}{120}\)

d) \(\dfrac{3}{5}-x=\dfrac{1}{4}+\dfrac{7}{10}\)

\(\Rightarrow\dfrac{3}{5}-x=\dfrac{19}{20}\)

\(\Rightarrow x=\dfrac{3}{5}-\dfrac{19}{20}\)

\(\Rightarrow x=\dfrac{-7}{20}\)

e) \(\dfrac{-3}{7}-x=\dfrac{4}{5}+\dfrac{-2}{3}\)

\(\Rightarrow\dfrac{-3}{7}-x=\dfrac{2}{15}\)

\(\Rightarrow x=\dfrac{-3}{7}-\dfrac{2}{15}\)

\(\Rightarrow x=\dfrac{-59}{105}\)

16 tháng 8 2023

g) \(\dfrac{-5}{6}-x=\dfrac{7}{12}+\dfrac{-1}{3}\)

\(\Rightarrow\dfrac{-5}{6}-x=\dfrac{1}{4}\)

\(\Rightarrow x=\dfrac{-5}{6}-\dfrac{1}{4}\)

\(\Rightarrow x=\dfrac{-13}{12}\)

a: =>x=-7/6+5/8=-13/24

b: =>x=-14/25-3/4=-131/100

c: \(x=\dfrac{-33}{26}:\dfrac{-9}{13}=\dfrac{33}{26}\cdot\dfrac{13}{9}=\dfrac{11}{3}\cdot\dfrac{1}{2}=\dfrac{11}{6}\)

d: \(x=\dfrac{4}{9}:\dfrac{5}{3}=\dfrac{4}{9}\cdot\dfrac{3}{5}=\dfrac{12}{45}=\dfrac{4}{15}\)

11 tháng 2 2018

a ) 5x=2y

b) 7x = 3y

c ) 3+x /7+y= 3/7

=> (3+x).7= (7+y).3

21 + 7x = 21 + 3y

=> 7x = 3y

=> x/y = 3/7 => x= 20:(7+3).3=6 

=> y = 20 - 6 = 14

Vậy (x;y) thuộc {(6;14)}

27 tháng 12 2022

a)\(\left(x+8\right)-11=20-15\)

\(\left(x+8\right)-11=5\)

\( x+8=5+11\)

\(x+8=16\)

\(x=8\)

b) \(2x-\left(3+x\right)=5-7\)

\(2x-\left(3+x\right)=-2\)

\(2x-3-x=-2\)

\(x=1\)

c) \( \left(3x-2^4\right)\times7^5=2\times7^6\)

\(3x-2^4=2\times\left(7^6:7^5\right) \)

\(\left(3x-2^4\right)=2\times7^2\)

\(3x-2^4=2\times49\)

\(3x-16=98\)

\(3x=114\)

\(x=38\)