1. A

2. B

3. A

4. B

1.    444 x 5 = 222 x 2 x 5 = 222 x 10 = 2220
2.    282 x 5 = 280 + 2 x 5 = 280 x 10 = 2800
3.    4 x 8 x 7 x 25 = (8 x 7) x (25 x4) = 56 x 100 = 5600
4.    25 x 8 x 9 = (25 x 4) x (4 x 9) = 100 x 36 = 3600
a.Đúng         b.Sai

1. sai

2. Sai

3. đúng

4.sai

1) Ta có: \(\left(-\dfrac{2}{3}\right)^2\cdot\dfrac{-9}{8}-25\%\cdot\dfrac{-16}{5}\)

\(=\dfrac{4}{9}\cdot\dfrac{-9}{8}-\dfrac{1}{4}\cdot\dfrac{-16}{5}\)

\(=\dfrac{-1}{2}+\dfrac{4}{5}\)

\(=\dfrac{-5}{10}+\dfrac{8}{10}=\dfrac{3}{10}\)

2) Ta có: \(-1\dfrac{2}{5}\cdot75\%+\dfrac{-7}{5}\cdot25\%\)

\(=\dfrac{-7}{5}\cdot\dfrac{3}{4}+\dfrac{-7}{5}\cdot\dfrac{1}{4}\)

\(=\dfrac{-7}{5}\left(\dfrac{3}{4}+\dfrac{1}{4}\right)=-\dfrac{7}{5}\)

3) Ta có: \(-2\dfrac{3}{7}\cdot\left(-125\%\right)+\dfrac{-17}{7}\cdot25\%\)

\(=\dfrac{-17}{7}\cdot\dfrac{-5}{4}+\dfrac{-17}{7}\cdot\dfrac{1}{4}\)

\(=\dfrac{-17}{7}\cdot\left(\dfrac{-5}{4}+\dfrac{1}{4}\right)\)

\(=\dfrac{17}{7}\)

4) Ta có: \(\left(-2\right)^3\cdot\left(\dfrac{3}{4}\cdot0.25\right):\left(2\dfrac{1}{4}-1\dfrac{1}{6}\right)\)

\(=\left(-8\right)\cdot\left(\dfrac{3}{4}\cdot\dfrac{1}{4}\right):\left(\dfrac{9}{4}-\dfrac{7}{6}\right)\)

\(=\left(-8\right)\cdot\dfrac{3}{16}:\dfrac{54-28}{24}\)

\(=\dfrac{-3}{2}\cdot\dfrac{24}{26}\)

\(=\dfrac{-72}{52}=\dfrac{-18}{13}\)

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

/x-3/=7-(-2)=9\(\Rightarrow x=9+3=12ho\text{ặc}x=-9+3=-6\)

(7-x)-(25+7)=-25\(\Rightarrow\left(7-x\right)-32=-25\Rightarrow7-x=-25+32=7\Rightarrow x=0\)

/x-3/=/5/+/-7/=5+7=12\(\Rightarrow x=15ho\text{ặc}x=-9\)

/x-5/=/-7/=7\(\Rightarrow x=12ho\text{ặc}x=-2\)

4-(7-x)=x-(13-4)\(\Rightarrow x-3=x-9\Rightarrow x-x=-9+3\Rightarrow0=-6\)(vô lí)

Vậy không có x thoả mãn 4-(7-x)=x-(13-4)

|x+2|=0

Vì |0|=0,suy ra x+2=0

                         x=0-2

                         x=-2

Vậy x = -2

|x-3|=7-(-2)

|x-3|=7+2

|x-3|=9

Vì |9|=|-9|=9,suy ra x-3 thuộc{9;-9}

*x-3=9

x   =9+3

x   =12

*x-3=-9

    x=-9+3

     x=-6

Vậy x thuộc {12;-6}

(7-x)-(25+7)=-25

(7-x)-32      =-25

            7-x =-25+32

            7-x  =57

              x   =7-57

              x   =7+(-57)

              x    =-50

vậy x=-50

|x-3|=|5|+|-7|

|x-3|=5+7

|x-3|=12

Vì |12|=|-12|=12,suy ra x-3 thuộc {12;-12}

*x-3=12

  x=12+3

  x=15

*x-3=-12

    x=-12+3

    x=-9

vậy x thuộc {15;-9}

giong minh

a: =>5-x=-23

=>x=5+23=28

b: =>x-3-x+7-25+x=54

=>x-21=54

=>x=75

c: =>7-9x-2x+4=-5x-35+27-25=-5x-37

=>-11x+3=-5x-37

=>-6x=-40

=>x=20/3

a) \(10-x-5=\left(-5\right)-7-11\)

\(\Rightarrow5-x=-23\)

\(\Rightarrow x=5+23\)

\(\Rightarrow x=28\)

b) \(\left(x-3\right)-\left(x+17-24\right)-\left(25-x\right)=24-\left(-30\right)\)

\(\Rightarrow x-3-x-17+24-25+x=54\)

\(\Rightarrow x-21=54\)

\(\Rightarrow x=54+21\)

\(\Rightarrow x=75\)

c) \(\left(7-9x\right)-\left(2x-4\right)=-\left(5x+35\right)-\left(-27\right)-25\)

\(\Rightarrow7-9x-2x+4=-5x-35+27-25\)

\(\Rightarrow11-11x=-5x-33\)

\(\Rightarrow-11x+5x=-33-11\)

\(\Rightarrow-6x=-22\)

\(\Rightarrow x=\dfrac{22}{6}=\dfrac{11}{3}\)

a. 
10-x-5 = (-5) - 7 -11
=>5-x = 0
=>x=5
b
(x-3) - (x+17-24) - (25-x) = 24 - (-30)
=>x - 3 - x - 17 + 24 - 25 - x = 24 + 30
=>-x - 21 = 54
=>-x = 75
=>x = -75
c
(7 - 9x) - (2x - 4) = - (5x + 35) - (-27) - 25
=>7-9x - 2x + 4 = -5x - 35 + 27 - 35
=>11 - 11x + 5x = -43
=>16x = 11 + 43
=>16x = 54
=>x=4

7 x 8 = 56       16 : 2 = 8       36 : 6 = 6       49 : 7 = 7

2 x 5 = 10       72 : 8 = 9       9 x 3 = 27       63 : 7 = 9

6 x 4 = 24       25 : 5 = 5       4 x 8 = 32       7 x 5 = 35

7 x 8 = 56

2 x 5 = 10

6 x 4 = 24

16 : 2 = 8 

72 : 8 = 9

25 : 5 = 5

36 : 6 = 6

9 x 3 = 27

4 x 8 = 32

49 : 7 = 7

63 : 7 = 9

7 x 5 = 35

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

\(\Rightarrow x+2=0\)

\(\Rightarrow x=0-2\)

\(\Rightarrow x=-2\)

\(\left|x-5\right|=\left|-7\right|\)

\(\Rightarrow\left|x-5\right|=7\)

\(\Rightarrow\hept{\begin{cases}x-5=-7\\x-5=7\end{cases}}\Leftrightarrow\hept{\begin{cases}x=-7+5\\x=7+5\end{cases}}\Leftrightarrow\hept{\begin{cases}x=-2\\x=12\end{cases}}\)

\(\Rightarrow x\in\left\{-2;12\right\}\)

|x+2|=0

\(\Rightarrow\)x+2=0

\(\Rightarrow\)x= 0-2

\(\Rightarrow\)x= -2

Các bn ơi !Giúp mk đi!

Ai nhanh mk k nhé !

\(\left(7-x\right)-\left(25+7\right)=-25\Leftrightarrow7-x-25-7=-25\)

\(\Rightarrow\left(7-7\right)-x-25=-25\Rightarrow-x=\left(-25\right)+25=0\Rightarrow x=0 \)

\(x-\left[42+\left(-28\right)\right]=-8\Rightarrow x-\left(42-28\right)=-8\)

\(\Rightarrow x-14=-8\Leftrightarrow x=\left(-8\right)+14=6\)

\(|x-3|=|5|+|-7|\Rightarrow|x-3|=5+7=12\)

\(\Rightarrow\hept{\begin{cases}x-3=12\\x-3=-12\end{cases}}\Rightarrow\hept{\begin{cases}x=12+3=15\\x=\left(-12\right)+3=-9\end{cases}}\)

\(4-\left(7-x\right)=x-\left(13-4\right)\Rightarrow4-7+x=x-13+4\)

\(\Rightarrow\left(-3\right)+x=x-9\Leftrightarrow2x=\left(-3\right)-9=-12\Rightarrow x=-6\)