a)

− 12 . x = − 15 . − 4 − 12 − 12 . x = 60 − 12 − 12 . x = 48                x = 48 : − 12                x = − 4

b) 

− 9 . x + 3 = − 2 . − 7 + 16 − 9 . x + 3 = 14 + 16 − 9 . x + 3 = 30 − 9 . x           = 30 − 3 − 9 . x           = 27              x           = 27 : − 9              x           = − 3

c)

− 12 . x − 34 = 2 − 12 . x               = 2 + 34 − 12 . x               = 36                x                = 36 : − 12                x                = − 3

a)

− 12 . x = − 15 . − 4 − 12 − 12 . x = 60 − 12 − 12 . x = 48                x = 48 : − 12                x = − 4

b)

− 9 . x + 3 = − 2 . − 7 + 16 − 9 . x + 3 = 14 + 16 − 9 . x + 3 = 30 − 9 . x           = 30 − 3 − 9 . x           = 27              x           = 27 : − 9              x           = − 3

c) 

− 12 . x − 34 = 2 − 12 . x               = 2 + 34 − 12 . x               = 36                x                = 36 : − 12                x                = − 3

bài2 \(x\times\dfrac{15}{16}-x\times\dfrac{4}{16}=2\) 

     \(x\times\dfrac{11}{16}=2\) 

     \(x=2:\dfrac{11}{16}\) 

    \(x=\dfrac{32}{11}\)

Bài 1 : 

 \(\dfrac{x}{16}\times\left(2017-1\right)=2\)

          \(\dfrac{x}{16}\times2016=2\)

                      \(\dfrac{x}{16}=\dfrac{2}{2016}\)

                         \(x=\dfrac{2}{2016}\times16\)

                         \(x=\dfrac{1}{63}\)

1- (5\(\dfrac{4}{9}\) +x+7\(\dfrac{7}{18}\)) : 15\(\dfrac{3}{4}\) = 0 

1- (\(\dfrac{49}{9}+x+\dfrac{133}{18}\)) : \(\dfrac{63}{4}=0\) 

 (\(\dfrac{49}{9}+\dfrac{133}{18}\)+\(x\) ) : \(\dfrac{63}{4}\) = 1 - 0 

       (\(\dfrac{77}{6}\) + \(x\) ) : \(\dfrac{63}{4}\) = 1

         \(\dfrac{77}{6}+x\)         = 1 x \(\dfrac{63}{4}\) 

          \(\dfrac{77}{6}\) + \(x\)          = \(\dfrac{63}{4}\)

                  \(x\)            = \(\dfrac{63}{4}\) - \(\dfrac{77}{6}\)

                  \(x=\) \(\dfrac{35}{12}\)

a) x – 9 = -14

x = -14 + 9

x = -5

b) 2( x + 7 ) = -16

2( x + 7 ) = 2 . ( -8 )

x + 7 = -8

x = -8 – 7 = -15

c) | x – 9 | = 7

x – 9 = 7 hoặc x – 9 = -7

x = 7 + 9 hoặc x = -7 + 9

x = 16 hoặc x = 2

d) ( x – 5 )( x + 7 ) = 0

x – 5 = 0 hoặc x + 7 = 0

x = 5 hoặc x = -7

1: =>x^2+4x-21=0

=>(x+7)(x-3)=0

=>x=3 hoặc x=-7

2: =>(2x-5-4)(2x-5+4)=0

=>(2x-9)(2x-1)=0

=>x=9/2 hoặc x=1/2

3: =>x^3-9x^2+27x-27-x^3+27+9(x^2+2x+1)=15

=>-9x^2+27x+9x^2+18x+9=15

=>18x=15-9-27=-21

=>x=-7/6

6: =>4x^2+4x+1-4x^2-16x-16=9

=>-12x-15=9

=>-12x=24

=>x=-2

7: =>x^2+6x+9-x^2-4x+32=1

=>2x+41=1

=>2x=-40

=>x=-20

\(\Leftrightarrow\frac{x+4}{9}+\frac{x+11}{8}+\frac{x+16}{7}+\frac{x+19}{6}=10\)

\(\Leftrightarrow\left(\frac{x+4}{9}-1\right)+\left(\frac{x+11}{8}-2\right)+\left(\frac{x+16}{7}-3\right)+\left(\frac{x+19}{6}-4\right)=0\)

\(\Leftrightarrow\frac{x+4-9}{9}+\frac{x+11-16}{8}+\frac{x+16-21}{7}+\frac{x+19-24}{6}=0\)

\(\Leftrightarrow\frac{x-5}{9}+\frac{x-5}{8}+\frac{x-5}{7}+\frac{x-5}{6}=0\)

\(\Leftrightarrow\left(x-5\right)\left(\frac{1}{9}+\frac{1}{8}+\frac{1}{7}+\frac{1}{6}\right)=0\)

\(\Leftrightarrow x-5=0\)

\(\Leftrightarrow x=5\)

V...

3^4 . 9 .3^x = 3^7

3^4 . 3^2 . 3^x = 3^7

3^6 . 3^x = 3^7

3^x = 3

x = 1

4^x . 4^1 = 16

4^x = 16 : 4

 4^x =4

=> x=1

5^x : 5 = 25

5^x = 25 . 5 =125

=> x = 3