9. (x + 28) = 0

x + 28 = 0: 9

x + 28 = 0

x = 0 – 28

x = -28

Vậy x = -28. 

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

2x=23+5

2x=28

x=28:2

x=14

Vậy x=14

 b) 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

2x=23+5

2x=28

x=28:2

x=14

Vậy x=14

chắc vại ;-;

a: =>41-(2x-5)=720:40=18

=>2x-5=23

=>2x=28

=>x=14

b: =>100x+5050=5750

=>100x=700

=>x=7

a: =>41-(2x-5)=720:40=18

=>2x-5=23

=>2x=28

=>x=14

b: =>100x+5050=5750

=>100x=700

=>x=7

a,  2 3 x + 5 2 x = 2 5 2 + 2 3 - 33

8x+25x = 33

33x = 33

x = 1

b,  260 : x + 4 = 5 2 3 + 5 - 3 3 2 + 2 2

260:(x+4) = 5.13–3.13

x+4 = 260:26

x+4 = 10

x = 6

c,  720 : [ 41 - 2 x - 5 ] = 2 3 . 5

41–(2x–5) = 720:40

2x–5 = 41–18

2x = 28

x = 14

d,  3 2 - 2 x - 12 + 35 = 5 2 + 279 : 3 2

7(x–12)+35 = 56

7(x–12) = 21

x–12 = 3

x = 15

a, 128 – 3(x+4) = 23

b,  12 x - 4 3 . 8 3 = 4 . 8 4

c, [(4x+28).3+55]:5 = 35

d, 720:[41 – (2x – 5)] =  2 3 . 5

720:[41-(2.x)]=23.5

720:[41-(2.x)]=115

       41-(2.x)=720:115

       41-(2.x)=\(\frac{144}{23}\)

            2.x=41-

2.x =41-\(\frac{144}{23}\)

2.x= \(\frac{799}{23}\)

x=\(\frac{799}{46}\)

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

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

(41-(2x))=1440/47

2x=41-1440/47

2x=487/47

x=481/47:2

x=481/94

\(\Leftrightarrow36-2x=36\)

=>x=0

x = 14

720: [41-(2x+5)]=8 x 5

720:[41-(2x+5)]=40

       41-(2x+5)=720:40

       41-(2x+5)=18

             2x+5=41-18

            2x+5=23

           2x    =23-5

            2x   =18

              x   =18:2

             x    =9

\(\left(25\cdot21+25\cdot51\right):36\\ =\left[25\cdot\left(21+51\right)\right]:36\\ =\left(25\cdot72\right):36\\ =1800:36\\ =50\\ \left\{188-\left[33+\left(6^2-7\cdot3\right)\right]\right\}:70\\ =\left\{188-\left[33+\left(36-21\right)\right]\right\}:70\\ =\left[188-\left(33+15\right)\right]:70\\ =\left(188-48\right):70\\ =140:70\\ =2\)

\(\left(x-1\right)\left(15-3x\right)=0\\ \Rightarrow\left[{}\begin{matrix}x-1=0\\15-3x=0\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=1\\3x=15\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=1\\x=5\end{matrix}\right.\)

\(720:\left[41-\left(2x+5\right)\right]=2^3\cdot5=8\cdot5\\ \Rightarrow720:\left[41-\left(2x+5\right)\right]=40\\ \Rightarrow41-\left(2x+5\right)=720:40\\ \Rightarrow41-\left(2x+5\right)=18\\ \Rightarrow2x+5=41-18\\ \Rightarrow2x+5=23\\ \Rightarrow2x=23-5\\ \Rightarrow2x=18\\ \Rightarrow x=18:2\\ \Rightarrow x=9\)

a) (25.21 + 25.51) : 36

= [ 25.( 21 + 51 ) ] : 36

= [ 25. 72 ] : 36

= 1800 : 36

= 50.

\(\Leftrightarrow41-2x+5=720:20=36\)

=>-2x=0

hay x=0