a) 72,5 - (2x + 1) = 630 : 9

⇒ 72,5 - (2x + 1) = 70

⇒ 2x + 1 = 2,5

⇒ 2x = 1,5

⇒ x = 0,75

b) (10 - 4x) + 120 : 2³ = 17

⇒ (10 - 4x) + 120 : 8 = 17

⇒ (10 - 4x) + 15 = 17

⇒ 10 - 4x = 2

⇒ 4x = 8

⇒ x = 2

Vậy x = 2

c) [124 - (20 - 4x)] : 30 + 7 = 11

⇒ [124 - (20 - 4x)] : 30 = 4

⇒ 124 - (20 - 4x) = 120

⇒ 20 - 4x = 4

⇒ 4x = 16

⇒ x = 4

Vậy x = 4

\(a\)\(.\)\(7^2.5-\left(2x+1\right)=630:9\)

\(49.5-\left(2x+1\right)=70\)

\(245-\left(2x+1\right)=70\)

                 \(2x+1=245-70\)

                  \(2x+1=175\)

                   \(2x=175-1\)

                   \(2x=174\)

                   \(x=174:2\)

                   \(x=87\)

Vậy \(x=87\)

\(b.\)\(\left(10-4x\right)+120:2^3=17\)

        \(\left(10-4x\right)+120:8=17\)

         \(\left(10-4x\right)+15=17\)

          \(10-4x=17-15\)

           \(10-4x=2\)

           \(4x=10-2\)

            \(4x=8\)

            \(x=8:4\)

            \(x=2\)

Vậy \(x=2\)

\(c.\)\(\left[124-\left(20-4x\right)\right]:30+7=11\)

\(\left[124-\left(20-4x\right)\right]:30=11-7\)

\(\left[124-\left(20-4x\right)\right]:30=4\)

\(\left[124-\left(20-4x\right)\right]=4.30\)

\(\left[124-\left(20-4x\right)\right]=120\)

\(124-20+4x=120\)

\(104+4x=120\)

\(4x=120-104\)

\(4x=16\)

\(x=16:4\)

\(x=4\)

Vậy \(x=4\)

\(d.\)\(\left|2x+5\right|=1\)

\(\Rightarrow2x+5\in\left\{-1;1\right\}\)

\(\Rightarrow2x\in\left\{-6;-4\right\}\)

\(\Rightarrow x\in\left\{-3;-2\right\}\)

Vậy \(x\in\left\{-3;-2\right\}\)

học tốt

a) \(7^2\cdot5-\left(2x+1\right)=630:9\)

\(\Leftrightarrow49\cdot5-2x-1=70\)

\(\Leftrightarrow244-2x=70\)

\(\Leftrightarrow2x=244-70\)

\(\Leftrightarrow2x=174\)

\(\Leftrightarrow x=87\)

Vậy x=87.

b) \(\left(10-4x\right)+120:2^3=17\)

\(\Leftrightarrow10-4x+120:8=17\)

\(\Leftrightarrow10-4x+15=17\)

\(\Leftrightarrow25-4x=17\)

\(\Leftrightarrow4x=25-17=8\)

\(\Leftrightarrow x=2\)

Vậy x=2

c)\([124-\left(20-4x\right)]:30+7=11\)

\(\Leftrightarrow\left(124-20+4x\right):30=4\)

\(\Leftrightarrow104+4x=120\)

\(\Leftrightarrow4x=120-104=16\)

\(\Leftrightarrow x=4\)

Vậy x=4

d) \(|2x-5|=1\)

\(\Leftrightarrow\orbr{\begin{cases}2x-5=1\\2x-5=-1\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}2x=6\\2x=4\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=3\\x=2\end{cases}}\)

Vậy \(x\in\text{ }\left\{3;2\right\}\)

Sorry mình ghi nhầm đề bài phần d

a) \(6x-36=5^{12}:5^{10}-2012^0\)

\(6x-36=5^2-2012^0\)

\(6x-36=25-1\)

\(6x-36=24\)

\(6x\) \(=24+36\)

\(6x\) \(=60\)

\(x=60:6\)

\(x=10\)

Vậy \(x=10\)

b) \(2x-125=-65\)

\(2x\) \(=\left(-65\right)+125\)

\(2x\) \(=60\)

\(x=60:2\)

\(x=30\)

Vậy \(x=30\)

c) \(2012-120\left(4x+1\right)=932\)

\(120\left(4x+1\right)=2012-932\)

\(120\left(4x+1\right)=1080\)

\(4x+1=1080:120\)

\(4x+1=9\)

\(4x\) \(=9-1\)

\(4x\) \(=8\)

\(x=8:4\)

\(x=2\)

Vậy \(x=2\)

a) 6x - 36 = 5¹² : 5¹⁰ - 2012⁰

6x - 36 = 5² - 2012⁰

6x - 36 = 25 - 1

6x - 36 = 24

6x = 24 + 36

6x = 60

x = 60 : 6

x = 10

Vậy x = 10

b) 2x - 125 = -65

2x = (-65) + 125

2x = 60

x = 60 : 2

x = 30

Vậy x = 30

c) 2012 - 120(4x + 1) = 932

120(4x + 1) = 2012 - 932

120(4x + 1) = 1080

4x + 1 = 1080 : 120

4x + 1 = 9

4x = 9 - 1

4x = 8

x = 8 : 4

x = 2

Vậy x = 2.

Chúc bạn học tốt!

TBR, Ta có: 

(100 – 4x) + 120 : 2³ = 1 + 4²  

 \(\Rightarrow\) 10 – 4x + 15 = 17

        = 25 – 4x = 17 \(\Rightarrow\)  4x = 25 – 17 \(\Rightarrow\) 4x = 25 – 17

\(\Rightarrow\)  4x = 8  \(\Rightarrow\)x = 8 : 4 = 2

\(\left(10-4x\right)+120:2^3=1+4^2\)

\(\Rightarrow\) \(\left(10-4x\right)+120:8=17\)

\(\Rightarrow\) \(\left(10-4x\right)+15=17\)

\(\Rightarrow\) \(10-4x=2\)

\(\Rightarrow\) \(4x=8\)

\(\Rightarrow\) \(x=2\)

(10 - 4x) + 120 : 2³ = 1 + 4²

(10 - 4x) + 120 : 2³ = 1 + 16 = 17

(10 - 4x) + 120 : 8 = 17

(10 - 4x) +   15      = 17

10 - 4x                   = 17 - 15 = 2

       4x                   = 10 - 2 = 8

         x                   = 8 : 4

         x                   = 2

Vậy x = 2

Good Luck!

a)(x-35)-120=0                            b)124+(118-x)=217                             c)156-(x+61)=82

x-35          = 0+120=120                118-x         =217-124=93                     x+61        = 156-82=74

x              = 120+35=155               x               = 118-93=25                     x              =74-61=13

suy ra x=155                                suy ra x= 25                                       suy ra x=13

a) ( x - 35 ) - 120 = 0

<=> x - 35 = 120

<=> x = 155

b) 124 + ( 118 - x ) = 217

<=> 118 - x = 93

<=> x = 25

c) 156 - ( x + 61 ) = 82

<=> x + 61 = 74

<=> x = 13

(x-35)-120=0

x-35         = 0 + 120

x-35          = 120

x               = 120 + 35

x                = 155

124+(118-x)=217

         118-x = 217-124

          118-x = 93

                x = 118 - 93

                x = 25

156-(x+61)=82

        x + 61=156-82

         x+61  = 74

          x        = 74 - 61

            x       = 13

(x-35)-120=0

x-35 = 0+120

x-35 = 120

x = 120-35

x = 85

124 + (118-x)=217

118-x=217-124

118-x=93

x=118-93

x=25

156-(x+61)=82

x+161=156-82

x+161=74

x=161-74

x=87

do la bai cua minh,co cho sai nao thi sua cho minh nhe

a,(x-35)-120=0
    x-35=120
    x=155
b,124+(118-x)=217
118-x=217-124
 118-x=  93
       x=25
c,156-(x+61)=82
    x+61=156-82
     x+61=74
x=13
 P/S: Bạn Hãy k hộ mk nha ^.^

gõ latex đi bn!

a. 2^x + 70 = 74

<=> 2^x = 4

<=> x = 2

b. 120 - \(\dfrac{4x}{2}\) = 80

<=> 120 - 2x = 80

<=> 120 - 80 = 2x

<=> 2x = 40

<=> x = 20

c. (3x + 5)² = 400

<=> \(|3x+5|=\sqrt{400}\)

<=> \(|3x+5|=20\)

<=> \(\left[{}\begin{matrix}3x+5=20\\3x+5=-20\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=5\\x=\dfrac{-25}{3}\end{matrix}\right.\) 

a) ( x - 35 ) - 120 = 0

<=> x - 35 = 120

<=> x = 155

b) 124 + ( 118 - x ) = 217

<=> 118 - x = 93

<=> x = 25

a, (x - 35) - 120 = 0

=> x - 35 = 120

=> x = 155

b, 124 + (118 - x) = 217

=> 118 - x = 93

=> x = 25

c, 156 - (x + 61) = 82

=> x + 61 = 74

=> x = 13

a) x = 155

b) x = 25

c) x = 13