123-5.(x+4)=38

 5(x+4)=123-38

 5(x+4)=85

 x+4=85:5

 x+4=17

 x=17-4

 x=13

10+2x=2.(3²-1)

 10+2x=2.(9-1)

 10+2x=2.8

 2x=16-10

2x=6

 x=6:2

 x=3

2.x-138=2³.3²

 2.x-138=72

 2.x=72+138

 2.x=210

 x=210:2

 x=105

[102+(28-2x)]:20-5=1

 (102+28-2x):20=6

 130-2x=120

 2x=130-120

 2x=10

 x=10:2

 x=5

231-(x-6)=1339:13

 231-(x-6)=103

 x-6=231-103

 x-6=128

 x=128+6

 x=134

123-5.(x+4)=38

5.(x+4)=123-38

5.(x+4)=85

(x+4)=85/5

x+4=17

x=17-4

x=13

10 + 2x = 2(3² - 1)

=> 10 + 2x = 2(9 - 1)

=> 10 + 2x = 2.8

=> 10 + 2x = 16

=> 2x = 16 - 10

=> 2x = 6

=> x = 6/2

=> x = 3

a)13-2(x+1)=7

  2.(x+1)=13-7

  2.(x+1)=6

  x+1=6/2

  x+1=3 

  x=3-1

  x=2

a, 13 - 2 ( x + 1 ) = 7

          2 .( x + 1 ) = 13 - 7
          2 .( x + 1 ) = 6
                x + 1   = 6 : 2
                x + 1    = 3
                x          = 3 - 1
                x           = 4

b)6x+2.4=5².2

6x+2=50

6x=48

x=8

c)420+65.4=(x+175):5+30

(x+175):5+30=680

(x+175):5=650

x+175=3250

x=3075

bn ơi chỗ 4 mũ 5 là nhân à

a) \(6-2\left(x+4\right)=-4\)

\(\Leftrightarrow6-2x-8=-4\)

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

\(\Leftrightarrow-2x=-4+2\)

\(\Leftrightarrow-2x=-2\)

\(\Leftrightarrow x=1\)

Vậy \(x=1\)

b) tự làm.

c) \(2x-15:5=-7\)

\(\Leftrightarrow2x-7,5=-7\)

\(\Leftrightarrow2x=-7+7,5\)

\(\Leftrightarrow2x=0,5\)

\(\Leftrightarrow x=0,25\)

\(\Leftrightarrow x=\dfrac{1}{4}\)

Vậy \(x=\dfrac{1}{4}\)

d) \(231-\left(x-6\right)=1339:13\)

\(\Leftrightarrow231-x+6=103\)

\(\Leftrightarrow237-x=103\)

\(\Leftrightarrow237-x+6=103\)

\(\Leftrightarrow-x=103-237\)

\(\Leftrightarrow-x=-134\)

\(\Leftrightarrow x=134\)

e) đề j mà có 2 dấu bằng >> sai :v

f) \(28-x^3=1\)

\(\Leftrightarrow-x^3=1-28\)

\(\Leftrightarrow-x^3=-27\)

\(\Leftrightarrow x^3=27\)

\(\Leftrightarrow x^3=3^3\)

\(\Leftrightarrow x=3\)

Vậy \(x=3\)

g) \(\left(x+2\right)^3=27\)

\(\Leftrightarrow\left(x+2\right)^3=3^3\)

\(\Leftrightarrow x+2=3\)

\(\Leftrightarrow x=3-2\)

\(\Leftrightarrow x=1\)

Vậy \(x=1\)

h) \(81-\left(x-5\right)^2=56\)

\(\Leftrightarrow-\left(x-5\right)^2=56-81\)

\(\Leftrightarrow-\left(x-5\right)^2=-25\)

\(\Leftrightarrow\left(x-5\right)^2=25\)

\(\Leftrightarrow x-5=\pm5\)

\(\Leftrightarrow\left[{}\begin{matrix}x-5=5\\x-5=-5\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=5+5\\x=-5+5\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=10\\x=0\end{matrix}\right.\)

Vậy \(x_1=0;x_2=10\)

j) \(x^2=9\)

\(\Leftrightarrow x=\pm3\)

\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-3\end{matrix}\right.\)

Vậy \(x_1=-3;x_2=3\)

l) tự làm.

a,70 – 5.(x – 3) = 45

5.(x -3) = 70 - 45

5.(x – 3) = 25

x – 3 = 25 : 5

x – 3 = 5

x = 5 + 3

x = 8

Vậy x = 8

b,\(2x-138=8x9=72\)

\(2x=138+72=210\)

\(x=210:2=105\)

c,\(10+2x=4^2\)\(=16\)

\(2x=16-10=6\)

\(x=6:2=3\)

d, 231 – (x- 6) = 1339 : 13

231 – (x – 6) = 103

x – 6 = 231 – 103

x – 6 = 128

x = 128 + 6

x = 134

Vậy x = 134

1+40/x=21

40/x=21-1

40/x=20

x=40/20

x=2

a) \(6-2x-8=-4\Leftrightarrow2x=2\Leftrightarrow x=1\)

b) \(6⋮x\Rightarrow x=\left\{-6;-3;-2;-1;1;2;3;6\right\}\)

c) \(2x-3=-7\Leftrightarrow2x=-4\Leftrightarrow x=-2\)

d) \(231-x+6=103\Leftrightarrow x=124\)

e) hình như sai đề

f) \(x^3=27\Leftrightarrow x=3\)

g) \(x+2=3\Leftrightarrow x=1\)

h) \(\left(x+5\right)^2=25\Leftrightarrow x+5=5\Leftrightarrow x=0\)

i) \(x^2=9\Leftrightarrow\orbr{\begin{cases}x=-3\\x=3\end{cases}}\)

j) \(14⋮\left(x+3\right)\Rightarrow x=\left\{-17;-10;-5;-4;-2;4;11\right\}\)

a) 70 - 5 (x - 3) = 45

 5 (x - 3) =70-45

 5 (x - 3) =25

 (x - 3)=25:5

 (x - 3)=5

x=5+3

x=8

b) 10 + 2.x = 4^5 : 4^3

10 + 2.x=4^2

10 + 2.x=16

2.x=16-10

2.x=6

x=6:2

x=3

c) 2x - 138 = 2^3 . 3^2

2x - 138 = 8.9

2x - 138 = 72

2x=72+138

2x=210

x=210:2

x=105

d) 231 - (x - 6) = 133 : 13

 (đề sai)