th1: x<-2 => 2(-x-2)+4-x=11 <=> -3x=11  => x=-11/3 (t/m đk)

th2: \(-2\le x\le4\)=> 2x+4+4-x=11 <=> x=3(t/m đk)

th3: x>4 => 2x+4+x-4=11 <=> 3x=11 <=> 11/3 (t/m đk)

=> x=11/3; x=-11/3 hoặc x=3

b. Ta có: \(2x=3y\Rightarrow\frac{x}{3}=\frac{y}{2}\Rightarrow\frac{x}{15}=\frac{y}{10}\) (1)

\(4y=5z\Rightarrow\frac{y}{5}=\frac{z}{4}\Rightarrow\frac{y}{10}=\frac{z}{8}\)(2)

Từ (1) và (2) => \(\frac{x}{15}=\frac{y}{10}=\frac{z}{8}=\frac{x+y+z}{15+10+8}=\frac{11}{33}=\frac{1}{3}\)

\(\frac{x}{15}=\frac{1}{3}\Rightarrow x=\frac{1}{3}\cdot15=5\) \(\frac{y}{10}=\frac{1}{3}\Rightarrow y=\frac{1}{3}\cdot10=\frac{10}{3}\)

\(\frac{z}{8}=\frac{1}{3}\Rightarrow z=\frac{1}{3}\cdot8\Rightarrow z=\frac{8}{3}\)

c. Ta thấy: \(\left(x+2\right)^{n+1}\ge0,\left(x+2\right)^{n+11}\ge0\) với mọi x.

Mà \(\left(x+2\right)^{n+1}=\left(x+2\right)^{n+11}\Rightarrow x+2\in\left\{0,1,-1\right\}\)

TH1: x + 2 = 0 => x = 0 - 2 => x = -2

TH2: x + 2 = 1 => x = 1 - 2 => x = -1

TH3: x + 2 = -1 => x = -1 - 2 => x = -3

\(-4+x=-4+7\)

\(\Rightarrow x=-4+7+4\)

\(\Rightarrow x=7\)

\(\left(-3\right)-\left(-5-x\right)=-15+\left(-6+15\right)\)

\(\Rightarrow x=-15-6+15+3-5\)

\(\Rightarrow x=-8\)

\(-\left(x+2\right)+2=\left(8-15\right)+15\)

\(\Rightarrow-x+2+2=-7+15\)

\(\Rightarrow-x=-7+15-2-2\)

\(\Rightarrow x=-4\)

\(4+\left(x-4\right)=-\left(11-2\right)+\left(11+4\right)\)

\(\Rightarrow4+x-4=-11+2+11+4\)

\(\Rightarrow x=-11+2+11+4-4+4\)

\(\Rightarrow x=6\)

a) -4 + x = -4 + 7            b) (-3) - (-5-x) = -15 + (-6+15)

   -4 + x + 4 - 7 = 0            (-3) + 5 + x = -6

        x - 7 = 0                     2 + 6 = -x

        x= 7                            8 = -x 

 Vậy x= 7                            x= -8   =) Vậy x= -8

c) -(x+2)+2=(8-15)+15          d) 4+(x-4)= -(11-2) + (11+4 )

   -x - 2 + 2 = 8                       4+x-4 = 6

   -x = 8                                     x=6

    x= -8                              Vậy x=6

Vậy x= -8

1: x=3/4-1/2=3/4-2/4=1/4

2: x-1/5=2/11

=>x=2/11+1/5=21/55

3: x-5/6=16/42-8/56

=>x-5/6=8/21-4/28=5/21

=>x=5/21+5/6=15/14

4: x/5=5/6-19/30

=>x/5=25/30-19/30=6/30=1/5

=>x=1

5: =>|x|=1/3+1/4=7/12

=>x=7/12 hoặc x=-7/12

6: x=-1/2+3/4

=>x=3/4-1/2=1/4

11: x-(-6/12)=9/48

=>x+1/2=3/16

=>x=3/16-1/2=-5/16

1)x= 1/4

2)x= 2/11+ 1/5

   x= 21/55

3)x - 5/6 = 5/21

   x         = 5/21+5/6

   x         = 15/14

4)x/5 = 5/6 + -19/30

   x:5 = 1/5

   x    = 1/5.5

   x    = 1

5) |x| - 1/4 = 6/18

    |x|           = 6/18 - 1/4

    |x|            =7/12

⇒x= 7/12 hoặc -7/12

6)x = -1/2 +3/4

   x= 1/4

7) x/15 = 3/5 + -2/3

   x:15  = -1/15

  x        = -1/15. 15

  x        = -1

8)11/8 + 13/6 = 85/x  

       85/24      = 85/x

  ⇒      x           = 24

9) x - 7/8 = 13/12

   x          = 13/12 + 7/8

   x          = 47/24

10)x - -6/15 = 4/27  

     x            = 4/27 + (-6/15)

    x             = -34/135

11) -(-6/12)+x = 9/48

                    x= 9/48 - 6/12

                    x = -5/16

12) x - 4/6 = 5/25 + -7/15

      x -4/6  =  -4/15

     x           = -4/15 + 4/6

    x             = 2/5