a.(2600+6400)-3.x=1200

9000-3.x=1200

3.x=9000-1200

3.x=7800

x=7800/3

x=2600

Vậy x=2600

b.[(6.x-72):2-84].28=5628

(6.x-72):2-84=5628:28

(6.x-72):2-84=201

(6.x-72):2=201+84

(6.x-72):2=285

6.x-72=285.2

6.x-72=570

6.x=570+72

6.x=642

x=642:6

x=107

vậy x=107

c.2x-138=\(2^3\).\(3^2\)

2x-138=8.9

2x-138=72

2x=72+138

2x=210

x=210:2

x=105

vậy x=105

a) Xem lại đề.

b) 5. (x - 3)² + 17 = 142

5. (x - 3)² = 142 - 17

5. (x - 3)² = 125

(x - 3)² = 125 : 5

(x - 3)² = 25

(x - 3)² = 5² (cùng số mũ)

⇒ x - 3 = 5

x = 5 + 3 = 8

c) [(6x - 72) : 2 - 84] . 28 = 5628

[(6x - 72) : 2 - 84] = 5628 : 28

[(6x - 72) : 2 - 84] = 201

(6x - 72) : 2 = 201 + 84

(6x - 72) : 2 = 285

6x - 72 = 285. 2

6x - 72 = 570

6x = 570 + 72

6x = 642

x = 642 : 6

x = 107

a,(2600+6400)-3 .x = 1200

=> 9000-3 .x= 1200

=> 3.x= 7800

=. x=2600

b, (6.x-72):2-84= 201

(6x-72):2=285

6x-72=570

6x=642

x=107

a) ( 2600 + 6400 ) - 3 . x = 1200

             9000       - 3 . x = 1200

                             3 . x = 9000 - 1200

                             3 . x =        7800

                                  x = 7800 : 3

                                  x =        2600

Ban kia lam dung roi do 

k tui nha

thanks

a) x = 7797

a) \(\left(2600+6400\right)-3-x=1200\)

\(\Rightarrow9000-3-x=1200\)

\(\Rightarrow3-x=9000-1200\)

\(\Rightarrow3-x=7800\)

\(\Rightarrow x=7797\)

b) \(\left[\left(6\cdot x-72\right):2-84\right]\cdot28=5628\)

\(\Rightarrow\left[\left(6\cdot x-72\right):2-84\right]=5628:28\)

\(\Rightarrow\left[\left(6\cdot x-72\right):2-84\right]=201\)

\(\Rightarrow\left(6\cdot x-72\right):2=201+84\)

\(\Rightarrow\left(6\cdot x-72\right):2=285\)

Đến dei bạn tự làm, ý b mình không chắc chắn lắm

x=107

a) (2600 + 6400) - 3 . x = 1200

           9000 - 3.x         = 1200

                  3x             = 9000-1200

                  3x             =  7800

                    x             = 7800:3

                    x             = 2600

b) câu này ko có tổng hả Công chúa nhí nhảnh? check lại giùm Nhi nha!

a)  \(\left(2600+6400\right)-3x=1200\)

\(9000-3x=1200\)

\(3x=9000-1200\)

\(3x=7800\)

\(x=\frac{7800}{3}\)

\(x=2600\)

vậy \(x=2600\)

b) \(\left[\left(6x-72\right):2-84\right].28+5628=0\)

\(\left[\frac{6x}{2}-\frac{72}{2}-84\right].28+5628=0\)

\(\left[3x-36-84\right].28=-5628\)

\(3x-120=\frac{-5628}{28}\)

\(3x-120=-201\)

\(3x=-201+120\)

\(3x=-81\)

\(x=-27\)

vậy \(x=-27\)

Ban kia lam dung roi do 

k tui nha

thanks

 A )123 -5 ( x -4 ) = 38

=> x-4 = (123-38) :(-5)

=> x-4=-17

=> x= -17+4=-13

B ) ( 3x - 2⁴ ) 7³ = 2.7⁴

=> 3x-16= 2.7⁴ :7³=14

=> 3x=14+16=30

=> x=30:3=10

C ) ( 2600 + 6400 ) - 3x = 1200

=> 9000-3x=1200

=> 3x=9000-1200=7800

=> x=7800:3=2600

D ) [( 6x - 72 ) : 2 - 84 ] 28 = 5628

=> (6x-72) :2-84= 5628:28=201

=> 6x-72 = (201+84) .2=570

=> 6x=570 +72=642

=> x= 642:6=107

( L-IKE )

A) 123 - 5(x-4) = 38

   5(x-4) = 123 - 38

   x-4 = 85 : 5

   x = 17 + 4

   x= 21

B) (3x - 2⁴)7³ = 2.7⁴

    (3x - 2⁴) = 2.7⁴:7³

     3x = 14 + 2⁴

    x = 30 : 3 = 10

 C) (2600 + 6400) - 3x = 1200

      9000 - 3x = 1200

      3x = 9000 - 1200 

      x = 7800 : 3 = 2600

D) [(6x - 72) : 2 - 84].28 = 5628

     (6x - 72) : 2 - 84 = 5628 : 28 = 201

     (6x - 72) : 2 = 201 + 84 = 285

     6x - 72 = 285 . 2 = 570

     6x = 570 + 72 = 642

     x = 642 : 6 = 107   

Có thể thử lại đáp án

#)Giải :

\(123-5\left(x+4\right)=38\)

\(\Leftrightarrow5\left(x+4\right)=85\)

\(\Leftrightarrow x+4=17\)

\(\Leftrightarrow x=13\)

\(\left(3x-16\right)343=2.2401\)

\(\Leftrightarrow\left(3x-16\right)343=4802\)

\(\Leftrightarrow3x-16=14\)

\(\Leftrightarrow3x=30\)

\(\Leftrightarrow x=10\)

\(\left(2600+6400\right)-3x=1200\)

\(\Leftrightarrow9000-3x=1200\)

\(\Leftrightarrow3x=7800\)

\(\Leftrightarrow x=2600\)

P/s : Câu cuối cùng lỗi chỗ b4 ph k ? hay là tìm cả b và x thế ???

\(123-5\left(x+4\right)=38\)

\(=>123-5x-20=38\)

\(=>-5x=-123+20+38\)

\(=>-5x=-65\)

\(=>x=13\)

b, \(\left(3x-16\right)343=2.2401\)

=>1029x -5488= 4802

=> 1029x=5488+4802

=> 1029x= 10290

=> x=10

c, (2600+6400)-3x=1200

=> 9000-3x=1200

=> -3x= -9000+1200

=> -3x= -7800

=> x=2600

d,

k hiểu đề

xin lỗi b4 sữa lại 84 nha