a) \(\frac{45-\left(3x+9\right)}{13}=42\)

\(\Leftrightarrow45-\left(3x+9\right)=546\)

\(\Leftrightarrow3x+9=-501\)

\(\Leftrightarrow3x=-510\)

\(\Leftrightarrow x=-170\)

b) \(\left(x+1\right)+\left(2x+2\right)+...+\left(20x+20\right)=1050\)

\(\Leftrightarrow x+1+2x+2+...+20x+20=1050\)

\(\Leftrightarrow\left(x+1\right)+2\left(x+1\right)+....+20\left(x+1\right)=1050\)

\(\Leftrightarrow\left(x+1\right)\left(1+2+3+...+20\right)=1050\)

\(\Leftrightarrow\left(x+1\right)\left[\frac{\left(20+1\right).20}{2}\right]=1050\)

\(\Leftrightarrow\left(x+1\right).210=1050\)

\(\Leftrightarrow x+1=5\)

\(\Leftrightarrow x=4\)

\(6^2-\left(x+3\right)=45\)

\(36-\left(x+3\right)=45\)

\(x+3=35-45\)

\(x+3=-10\)

\(x=-13\)

lớp 6 mà bạn

\(6^2-\left(x+3\right)=45\)

\(\Rightarrow36-\left(x+3\right)=45\)

\(\Rightarrow x+3=36-45\)

\(\Rightarrow x+3=-9\)

\(\Rightarrow x=-9-3=-12\)

\(125-5\left(3x-1\right)=5^5.5^3\)

\(\Rightarrow5^3-5\left(3x-1\right)=5^5.5^3\)

\(\Rightarrow5^3-15x+5=5^5.5^3\)

\(\Rightarrow5\left(5^2-3x+1\right)=5^5.5^3\)

\(\Rightarrow5^2-3x+1=5^5.5^3:5\)

\(\Rightarrow25-3x+1=5^7\)

Từ đây làm nốt nhé

\(4^x+1+4^0=65\)

\(\Rightarrow4^{x+1}+1=65\)

\(\Rightarrow4^{x+1}=64\)

\(\Rightarrow4^{x+1}=4^3\)

\(\Rightarrow x+1=3\)

\(\Rightarrow x=2\)

\(70-5\left(x-3\right)=5.3^2\)

\(\Rightarrow70-5\left(x-3\right)=5.9=45\)

\(\Rightarrow5\left(x-3\right)=70-45=25\)

\(\Rightarrow x-3=25:5=5\)

\(\Rightarrow x=8\)

Chúc em học tốt hơn nhé!!

a,

x-43+7=49-(50+3)

<=>x-36=49-53

<=>x-36=-4

<=>x=-4+36

<=>x=32

b

-(x-16)+70=45

<=>-x+16+70=45

<=>-x+86=45

<=>x=86-45

<=>x=41

Bài 2

a.,

2x-(-60)=3x-18

<=>2x+60=3x-18

<=>3x-2x=60+18

<=>x=78

b,

-45-5x=10-4x

<=>-4x+5x=-45-10

<=>x=-55

Nếu thấy bài làm của mình đúng thì tick nha bạn,mình xin chân thành cảm ơn.

a) x-  43 + 7 = 49 - (50 + 3)

x - 36 = -4

x = -4 + 36

x = 32

b) -(x - 16) + 70 = 45

-(x - 16) = -15

x - 16 = 15

x = 31

Bài 2:

2x - (-60) = 3x - 18

2x + 60 = 3x - 18

3x - 2x = 60 + 18

x = 78

b) -4- 5x = 10 - 4x

5x - 4x = -4 - 10

x = -14

nguyenthihuyentrang

( 2x  - 5)²  - ( 4x - 1 ) ( x + 3 ) = 5 

=> ( 2x ) ²   - 2 . 2x. 5 + 5² - 4x² + 12x - 3 - x = 5 

=> 4x²    - 20x + 15 - 4x²  + 11x - 3 = 5 

=> -20x + 11x = 5 + 3 - 15 

=> -9x = -7  =>  x = 7/9 

^^ Học tốt! 

M.n giup mk vs ak!! mk se tag k cho m.n, camon ah!

ê sao ko cho 

\(trog.khug.ý\)

1) 5x = 120 : 2

5x = 60

x = 60 : 5

x = 12.

2) 3x + 27 = 45

3x = 45 - 27

3x = 18

x = 18 : 3

x = 6.

3) 73 + x - 122 = 234 : 2

73 + x - 122 = 117

73 + x = 117 + 122

73 + x = 239

x = 239 - 73

x = 166.

4) 32 - 2 ( x - 1 ) = 12

2 ( x - 1 ) = 32 - 12

2 ( x - 1 ) = 20

x - 1 = 20 : 2

x - 1 = 10

x = 10 + 1

x = 11.

5) 3 ( x + 1 ) - 15 = 36

3 ( x + 1 ) = 36 + 15

3 ( x + 1 ) = 51

x + 1 = 51 : 3

x + 1 = 17

x = 17 - 1

x = 16.

6) 32 - ( 4x - 16 ) = 21

4x - 16 = 32 - 21

4x - 16 = 11

4x = 11 + 16

4x = 27

x = 27 : 4

x = 6,75.

7) 13x - 3x = 500

( 13 - 3 )x = 500

10x = 500

x = 500 : 10

x = 50.

8) 9x + x - 35 = 68

9x + 1x - 35 = 68

9x + 1x = 68 + 35

9x + 1x = 103

( 9 + 1 )x = 103

10x = 103

x = 103 : 10

x = 10,3.

1) 5x = 120 : 2

5x = 60

x = 60 : 5

x = 12.

2) 3x + 27 = 45

3x = 45 - 27

3x = 18

x = 18 : 3

x = 6.

3) 73 + x - 122 = 234 : 2

73 + x - 122 = 117

73 + x = 117 + 122

73 + x = 239

x = 239 - 73

x = 166.

4) 32 - 2 ( x - 1 ) = 12

2 ( x - 1 ) = 32 - 12

2 ( x - 1 ) = 20

x - 1 = 20 : 2

x - 1 = 10

x = 10 + 1

x = 11.

5) 3 ( x + 1 ) - 15 = 36

3 ( x + 1 ) = 36 + 15

3 ( x + 1 ) = 51

x + 1 = 51 : 3

x + 1 = 17

x = 17 - 1

x = 16.

6) 32 - ( 4x - 16 ) = 21

4x - 16 = 32 - 21

4x - 16 = 11

4x = 11 + 16

4x = 27

x = 27 : 4

x = 6,75.

7) 13x - 3x = 500

( 13 - 3 )x = 500

10x = 500

x = 500 : 10

x = 50.

8) 9x + x - 35 = 68

9x + 1x - 35 = 68

9x + 1x = 68 + 35

9x + 1x = 103

( 9 + 1 )x = 103

10x = 103

x = 103 : 10

x = 10,3.

-3x-(-24)=-45

- 3x + 24 = -45

- 3x =-45-24

- 3x =-69

x= 69:3

x= 23

Vậy...

\(\frac{x}{7}\)= \(-\frac{6}{21}\)

=> 21 x = -6.7

21x = -42

x= -42:21

x= -2

Vậy...

\(\frac{x}{7}=-\frac{6}{21}\)

\(\Leftrightarrow x.21=7.\left(-6\right)\)

\(\Leftrightarrow x.21=-42\)

\(\Leftrightarrow x=-2\)

a) 5x = 120 : 2

5x = 60

x = 60 : 5

x = 12

b) 3x + 27 = 45

3x = 45 - 27

3x = 18

x = 18 : 3

x = 6

c) 73 + x - 122 = 234 : 2

73 + x - 122 = 117

73 + x = 117 + 122

73 + x = 239

x = 239 - 73

x = 166

d) 32 - 2(x - 1) = 12

2(x - 1) = 32 - 12

2(x - 1) = 20

x - 1 = 20 : 2

x - 1 = 10

x = 10 + 1

x = 11

e) 3(x + 1) - 15 = 36

3(x + 1) = 36 + 15

3(x + 1) = 51

x + 1 = 51 : 3

x + 1 = 17

x = 17 - 1

x = 16

f) 21 - (4x - 16) = 21

4x - 16 = 21 - 21

4x - 16 = 0

4x = 0 + 16

4x = 16

x = 16 : 4

x = 4

g) 13x - 3x = 500

10x = 500

x = 500 : 10

x = 50

h) 9x + x - 35 = 65

10x - 35 = 65

10x = 65 + 35

10x = 100

x = 100 : 10

x = 10

     -45:(3x-17)=3^2

⇒ -45:(3x-17)= 9

⇒ 3x-17         =-45:9

⇒3x-17          =-5

⇒3x               =-5+17

⇒3x               =12

⇒ x                = 12:3=4

Vậy: x=4