a, 36:(x–5) =  2 2

(x–5) = 9

x = 14

b, [3.(70–x)+5]:2 = 46

[3.(70–x)+5] = 92

70–x = 29

x = 41

c, 450:[41–(2x–5)] =  3 2 .5

41–(2x–5) = 10

2x–5 = 31

2x = 36

x = 18

d, 230+[ 2 4 +(x–5)] = 315. 2018 0

16+(x–5) = 315–230

x–5 = 85–16

x = 69+5

x = 74

e,  2 x + 2 x + 1  = 48

2 x .(2+1) = 48

2 x = 16 =  2 4

x = 4

f,  3 x + 2 + 3 x  = 2430

3 x . 3 2 + 1 = 2430

3 x = 2430:10 = 243 =  3 5

x = 5

b. 1500(x-7)=0

x-7=0

x=7

c. (2x-4)(48-12x)=0

2x-4=0 hoặc 48-12x=0

x=2 hoặc x=4

d. (x+12)(x-1)=0

x+12=0 hoặc x-1=0

x=-12 hoặc x=1

bài 2 :

a . 128-3(x+4)=23

3(x+4)=105

x+4=35

x=31

b. [(14X+26).3+55]:5=35

(14x+26).3+55=175

(14x+26).3=120

14x+26=40

14x=14

x=1

d. 720:[41-(2X-5)]=23.5

41-(2x-5)=720:(23.5)

41-(2x-5)=144/23

2x-5=799/23

2x=914/23

x=457/23

b, 1500.(x – 7) = 0

<=>1500x-10500=0

<=>1500x=10500

<=>x=7

Vậy x=7

c,(2.x – 4).(48 – 12.x) = 0

\(\Leftrightarrow\)\(\left\{{}\begin{matrix}2x-4=0\\48-12x=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2x=4\\12x=48\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=2\\x=4\end{matrix}\right.\)

Vậy x=2 hoặc x=4

d, (x + 12).(x – 1) =0

\(\Leftrightarrow\left\{{}\begin{matrix}x+12=0\\x-1=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-12\\x=1\end{matrix}\right.\)

Vậy x=-12 hoặc x=1

Bài 2:

a) 128- 3(x+ 4) = 23

\(\Leftrightarrow\)128-(3x+12)=23

\(\Leftrightarrow\)128-3x-12=23

\(\Leftrightarrow\)116-3x=23

\(\Leftrightarrow\)3x=116-23

\(\Leftrightarrow\)3x=93

\(\Leftrightarrow\)x=31

Vậy x=31

b) [(14x+ 26). 3+ 55]: 5= 35

\(\Leftrightarrow\)(14x+ 26). 3+ 55=175

\(\Leftrightarrow\)42x+78+55=175

\(\Leftrightarrow\)42x+133=175

\(\Leftrightarrow\)42x=175-133

\(\Leftrightarrow\)42x=42

\(\Leftrightarrow\)x=1

Vậy x=1

d, 720: [41- (2x- 5)]= 23. 5

\(\Leftrightarrow\)720: 41- (2x- 5)=115

\(\Leftrightarrow\)41-(2x- 5)=720:115

\(\Leftrightarrow\)41-(2x- 5)=\(\dfrac{144}{23}\)

\(\Leftrightarrow\)2x-5=\(\dfrac{799}{23}\)

\(\Leftrightarrow\)2x=\(\dfrac{914}{23}\)

\(\Leftrightarrow\)x=\(\dfrac{457}{23}\)

Vậy x=\(\dfrac{457}{23}\)

1e) Để \(\frac{2x-1}{x-3}\) nguyên thì \(2x-1⋮x-3\)

\(\Leftrightarrow2x-6+5⋮x-3\)

\(\Leftrightarrow2\left(x-3\right)+5⋮x-3\)

Do \(2\left(x-3\right)⋮x-3\) \(\Rightarrow5⋮x-3\)

\(\Rightarrow x-3\in\left\{-5;-1;1;5\right\}\)

\(\Leftrightarrow x\in\left\{-2;2;4;8\right\}\)

Vậy:...................

720:[41-(2x - 5)]=2³.5

 720:[41-(2x - 5)]=8.5

 720:[41-(2x - 5)]=40

        41-(2x - 5)=720:40

        41-(2x - 5)=18

       2x - 5=41-18

       2x - 5=23

        2.x=23+5

        2.x=28

        x=28:2

        x=14

hello

sao hello xong ko help j ngt z ?

23+3x=125

3x=125-23

3x= 102

x= 102:3

x= 34

41-(2x-5)=18

2x-5=41-18

2x-5=23

2x=23+5

2x=28

x=28:2

x=14

\(720:\left(41-2x-5\right)=23,5\)

<=> \(41-2x-5=\frac{1440}{47}\)

<=> \(x=2,680851064\)

\(720:\left(41-2x-5\right)=23,5\)

\(\Leftrightarrow720:36-720:2x=23,5\)

\(\Leftrightarrow20-720:2x=23,5\)

\(\Leftrightarrow-720:2x=23,5-20\)

\(\Leftrightarrow-720:2x=3,5\)

\(\Leftrightarrow2x=\frac{-1440}{7}\)

\(\Leftrightarrow x=\frac{-720}{7}\)

720 : ( 41 - 2x - 5 ) = 23.5

41 - 2x - 5 = 720 : 23.5

41 - 2x - 5 = 1440/47

36 - 2x = 1440/47

2x = 36 - 1440/47

2x = 252/47

x = 252/47 : 2

x = 126/47

[ 41 -(2x -5)] = 2^3.5

[ 41 -(2x -5)] =  8.5

[ 41 -(2x -5)] = 40

       2x -5=    41 - 40

         2x -5   = 1

           2x      = 1 + 5

            2x =    6

             x   =   6 : 2 

               x    = 3

HOk tốt

\(41-\left(2x-5\right)=2^3.5\)

\(\Rightarrow41-\left(2x-5\right)=8.5\)

\(\Rightarrow41-\left(2x-5\right)=40\)

\(\Rightarrow2x-5=41-40\)

\(\Rightarrow2x-5=1\)

\(\Rightarrow2x=1+5\)

\(\Rightarrow2x=6\)

\(\Rightarrow x=6:2\)

\(\Rightarrow x=3\)

Vậy x = 3

_Chúc bạn học tốt_

\(41-\left(2x-5\right)=2^3.5\)

\(\Leftrightarrow41-2x+5=8.5\)

\(\Leftrightarrow-2x+5=40-41\)

\(\Leftrightarrow-2x+5=-1\)

\(\Leftrightarrow-2x=-1-5\)

\(\Leftrightarrow-2x=-6\)

\(\Leftrightarrow x=-6:\left(-2\right)=3\)

Vậy \(x=3\)

=> 41 - ( 2x - 5) = 720 : 160 = 6

=> 2x - 5 = 41 - 6 

=> 2x - 5 = 35

=>2x = 40 

=> x = 20

Vậy x = 20 

Ta co: 

720:[41-(2x-5)]=120

41-(2x-5)        = 720 : 120

41 - (2x-5)      = 6

 2x  - 5          = 41 -6

2x -5             = 35

2x                 = 35 +5

2x                 = 40

x                   = 40 :2

x                   =20

​Vậy x bằng 20 

720 : [ 41 - ( 2x - 5 ) ] = 120

=>    41 - ( 2x - 5 ) = 720 : 120 = 6

=>          2x - 5 = 41 - 6 = 35

=>              2x = 35 + 5 = 40

=>                 x = 40 : 2 = 20

đúng nha !!!