dấu / / là giá trị tuyệt đối

a) / x + 3 / = 15

=> x + 3 = 15 hay x + 3 = -15

TH1 : x + 3 = 15

           x =15 - 3

           x = 12

TH2 :  x + 3 = -5

             x = -5 - 3

             x = -8

VẬy : x thuộc { 12;-8 }

b ) /x-7/ + 13 = 25

      / x - 7 / = 25 - 13

      / x - 7 / = 12

   => x - 7 = 12 hay x -  7 = -12

TH1 : x - 7 = 12

         x = 12 + 7

         x =19

TH2: x - 7 = -12

          x = -12 + 7

          x = -5

Vậy : x thuộc { 19; -5 }

c) 3 ( x + 3 )² = 27

  ( x + 3 )² = 27 : 3

  ( x + 3 ) ² = 9

x + 3 = 3 hay x + 3 = -3 ( lũy thừa bậc chẵn )

Th1 : x + 3 = 3

         x = 3 -3 

         x = 0

TH2 : x + 3 = -3

           x = -3-3

       x = -6

Vậy : x thuộc { 0 ; -6 }

d) 20 - 2 ( 1-x )³ = 4

 2 ( 1 - x )³ = 20 - 4

 2 ( 1 - x )³ = 16

( 1 - x )³ = 16 : 2

 ( 1 -x )³ = 8

 ( 1 - x )³ = 2³ 

=> 1 - x = 2

   x = 1 - 2

   x = -1

VẬy : x = -1

a: =>2x-3x^2-x<15-3x^2-6x

=>x<-6x+15

=>7x<15

=>x<15/7

b: =>4x^2-24x+36-4x^2+4x-1>=12x

=>-20x+35>=12x

=>-32x>=-35

=>x<=35/32

\(a,2x-x\left(3x+1\right)< 15-3x\left(x+2\right)\\ \Leftrightarrow2x-3x^2-x< 15-3x^2-6x\\ \Leftrightarrow3x^2-3x^2+2x+6x-x< 15\\ \Leftrightarrow7x< 15\\ \Leftrightarrow x< \dfrac{15}{7}\)

Vậy S={-∞; 15/7}

\(b,4\left(x-3\right)^2-\left(2x-1\right)^2\ge12x\\ \Leftrightarrow4\left(x^2-6x+9\right)-\left(4x^2-4x+1\right)-12x\ge0\\ \Leftrightarrow4x^2-4x^2-24x+4x-12x\ge-36+1\\ \Leftrightarrow-32x\ge-35\\ \Leftrightarrow x\le\dfrac{35}{32}\)

Vậy S={-∞; 35/32]

\(a,\left[x+\frac{1}{3}\right]^3=-\frac{8}{27}\)

\(\Leftrightarrow\left[x+\frac{1}{3}\right]^3=\left[-\frac{2}{3}\right]^3\)

\(\Leftrightarrow x+\frac{1}{3}=-\frac{2}{3}\)

\(\Leftrightarrow x=-\frac{2}{3}-\frac{1}{3}=-1\)

Vậy x = -1

a) (x+1/3)³ = -8/27

<=> (x+1/3)³ = (-2/3)³

<=> x + 1/3 = -2/3

<=> x = -1

b) \(\frac{1}{4}x-\frac{8}{12}=1-\frac{3}{2}x\)

\(\Leftrightarrow\frac{7}{4}x=\frac{5}{3}\)

<=> x = 20/21

a,\(\left(x+\frac{1}{3}\right)^3=\frac{-8}{27}\)

\(\Leftrightarrow\left(x+\frac{1}{3}\right)^3=\left(-\frac{2}{3}\right)^3\)

\(\Leftrightarrow x+\frac{1}{3}=-\frac{2}{3}\)

\(\Leftrightarrow x=-\frac{2}{3}-\frac{1}{3}=-1\)

Vậy x = -1 

b, \(\frac{1}{4}x-\frac{8}{12}=1-\frac{3}{2}x\)

\(\Leftrightarrow\frac{3x-8}{12}=\frac{2-3x}{2}\)

\(\Leftrightarrow\left(3x-8\right)2=12\left(2-3x\right)\)

\(\Leftrightarrow6x-16=24-36x\)

\(\Leftrightarrow42x=40\)

\(\Leftrightarrow x=\frac{40}{42}=\frac{20}{21}\)

Vậy \(x=\frac{20}{21}\)

a: x^3=7^3

=>x^3=343

=>\(x=\sqrt[3]{343}=7\)

b: x^3=27

=>x^3=3^3

=>x=3

c: x^3=125

=>x^3=5^3

=>x=5

d: (x+1)^3=125

=>x+1=5

=>x=4

e: (x-2)^3=2^3

=>x-2=2

=>x=4

f: (x-2)^3=8

=>x-2=2

=>x=4

h: (x+2)^2=64

=>x+2=8 hoặc x+2=-8

=>x=6 hoặc x=-10

j: =>x-3=2 hoặc x-3=-2

=>x=1 hoặc x=5

k:

9x^2=36

=>x^2=36/9

=>x^2=4

=>x=2 hoặc x=-2

l:

(x-1)^4=16

=>(x-1)^2=4(nhận) hoặc (x-1)^2=-4(loại)

=>x-1=2 hoặc x-1=-2

=>x=3 hoặc x=-1

Bài giải:

b) 15 - 3 . |2x - 1| = 6

=> 12 . |2x - 1| = 6

=> |2x - 1| = 6 : 12

=> |2x - 1| = 0,5

=> 2x - 1 = 0,5 hoặc 2x - 1 = -0,5

     2x - 1 = 0,5                                            2x - 1 = -0,5

     2x = 0,5 + 1                                           2x = -0,5 + 1

     2x = 1,5                                                 2x = 0,5

     x = 1,5 : 2 = 0,75                                    x = 0,5 : 2 = 0,25

Vậy x = {0,75 ; 0,25}

c)2.|x| - 7 = 27

=> 2.|x| = 27 + 7

=> 2.|x| = 34

=> |x| = 34 : 2

=> |x| = 17

=> x = 17 hoặc x = -17

b , 15 -3 | 2x -1  | = 6

3 | 2x -1 |             = 15 -6

3 | 2x -1 |            =9

|2x -1 |                = 9 : 3

|2x -1 |                =3

suy ra 2x -1 thuoc { 3 ; -3 }

xet 2 truong hop

truong hop 1

2x -1 = 3

2x     =3+1

2x     = 4

x       = 4 : 2

x      = 2

c , 2| x | - 7     = 27

2 | x |              =27+7

2 | x |              =    34

   | x |             = 34 :2

   | x |             = 17

suy ra x thuoc { 17 ; 17 }

chuc ban hoc tot

a)p(x)=x⁷-80x⁶+80x⁵-80x⁴+.........+80+15

=x⁷-(79+1)⁶+(79+1)⁵-(79+1)⁴+.........+(79+1)x+15

mà x=79

=> x⁷-(x+1)⁶+(x+1)⁵-(x+1)⁴+..........+(x+1)x+15

=x⁷-x⁷+x⁶-x⁶+x⁵-x⁵+........+x²+x+15

=x+15

=79+15

=94

Trả lời

100+98+96+...+2-1-3-...-95-97

=100+(98-97)+(96-95)+...+(4-3)+(2-1)

=100+1.49

=4900.

Học tốt !

Ô, sory bạn nha.

mk làm nhầm bài rùi.

HUHU !

ko sao đâu

\(a,30+X=120:5+27\\ 30+X=24+27\\ 30+X=51\\ X=51-30=21\\ ---\\ b,40-3\times X=13\\ 3\times X=40-13=27\\ X=\dfrac{27}{3}=9\\ ---\\ 2\times X-8=16\\ 2\times X=16+8\\ 2\times X=24\\ X=\dfrac{24}{2}=12\\ \\---\\ \dfrac{1}{2}\times X-\dfrac{1}{3}=\dfrac{1}{4}\\ \dfrac{1}{2}\times X=\dfrac{1}{4}+\dfrac{1}{3}=\dfrac{7}{12}\\ X=\dfrac{7}{12}:\dfrac{1}{2}=\dfrac{7}{6}\)

a.30+X=24+27

30+X=51

      X=51-30

       X=21

b.3xX=40-13

3xX=27

   X=27:3=9

C.2xX=16+8

2xX=24

 X=24:2=12

D.1/2xX=1/3+1/4

1/2xX=7/12

     X=7/12:1/2=7/6

a) \(30+x=120:5+27\)

\(30+x=24+27\)

\(30+x=51\)

\(x=51-30\)

\(x=21\)

_____

b) \(40-3\times x=13\)

\(3\times x=40-13\)

\(3\times x=27\)

\(x=27:3\)

\(x=9\)

______

c) \(2\times x-8=16\)

\(2\times x=16+8\)

\(2\times x=24\)

\(x=24:2\)

\(x=12\)

______

d) \(\dfrac{1}{2}\times x-\dfrac{1}{3}=\dfrac{1}{4}\)

\(\dfrac{1}{2}\times x=\dfrac{1}{4}+\dfrac{1}{3}\)

\(\dfrac{1}{2}\times x=\dfrac{7}{12}\)

\(x=\dfrac{7}{12}:\dfrac{1}{2}=\dfrac{7}{12}\times2\)

\(x=\dfrac{7}{6}\)