2x+12=3(x-7)

2x+12=3x-21

3x-2x=12+21

x=33

vậy x=33

2x + 12 = 3 ( x - 7 )

2x + 13 = 3x - 3. 7 

2x + 13 = 3x - 21

- 3x + 2x = -13 - 21

-1x = -34

x = -34 : ( - 1 )

x = 34

2x+12=3x-21

=>3x-2x=12+21

=>x=33

\(2x+12=3.\left(x-7\right)\)

\(=>2x+12=3x-21\)

\(=>-x=-21-12=-33\)

\(=>x=33\)

2x+12=3.(x-7)

<=>2x+12=3x-21

<=>2x-3x=-21-12

<=>-x=-33

<=>x=33

5.(x+7)=3.(2-x)

=>5x+35=6-3x

=>5x+3x=6+41

=>8x=47

=>x=47:8=47/8

\(12\left(x-3\right)=5\left(x-1\right)+4\)

\(\Rightarrow12x-36=5x-5+4\)

\(\Rightarrow12x-5x=-5+4+36\)

\(\Rightarrow7x=35\)

\(\Rightarrow x=5\)

\(-6\left(x-7\right)+2\left(x+10\right)=x-18\)

\(-6x+42+2x+20=x-18\)

\(-6x+2x-x=-18-20-42\)

\(-5x=-80\)

\(x=16\)

\(7\left(2x-1\right)-12\left(x-5\right)=3\)

\(\Rightarrow14x-7-12x+60=3\)

\(\Rightarrow14x-12x=3-60+7\)

\(\Rightarrow2x=-50\)

\(\Rightarrow x=-25\)

\(\left|2x-1\right|=17\)

\(\Leftrightarrow\orbr{\begin{cases}2x-1=17\\2x-1=-17\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=9\\x=-8\end{cases}}\)

\(\left|8-3x\right|=14\)

\(\Leftrightarrow\orbr{\begin{cases}8-3x=14\\8-3x=-14\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=-2\\x=\frac{22}{3}\end{cases}}\)

a)

 13/4+x=2

          x=2-13/4

         x=-5/4

b)

 2x.17/12=3/7

 2x          =3/7;17/12

 2x         =36/119

  x           =36/119 : 2

  x           =18/119

c)

 2x.17/12=19/7

 2x         =19/7:17/12

 2x         =228/119

   x         =228/119;2

   x         =114/119

d)

 1/2x + 5/6=-3

 1/2x         =-3-5/6

 1/2x         =-23/6

     x          =-23/6:1/2

    x          =-23/3

\(2x+12=3\left(x-7\right)\)

\(2x+12=3x-21\)

\(2x-3x=-21-12\)

          \(-x=-33\)

              \(x=33\)

\(\Leftrightarrow2x+12=3x-21.\)

\(\Leftrightarrow2x-3x=-21-12\)

\(\Leftrightarrow-x=-33\)

\(\Rightarrow x=33\)

Vậy \(x=33\)

2x²-1=49