\(\Leftrightarrow a\cdot\dfrac{13}{15}=\dfrac{28}{13}:2=\dfrac{14}{13}\)

=>\(a=\dfrac{14}{13}:\dfrac{13}{15}=\dfrac{210}{169}\)

\(\Leftrightarrow x^2-x-x^2+2x+3=2\)

=>x=-1

60%.\(x\) + 0,4.\(x\) + \(x\): 3 = 4

0,6\(x\) + 0,4\(x\) + \(\dfrac{1}{3}\)\(x\) = 4

(0,6 + 0,4 + \(\dfrac{1}{3}\)).\(x\) = 4

   \(\dfrac{4}{3}\).\(x\)                   = 4

       \(x\)                   = 4: \(\dfrac{4}{3}\)

      \(x\)                   = 3

??????????????????????????????????????????????????????????????????????????????????????????????????????????????????

\(60\%.x+0,4.x+x:3=4\)

\(0,6x+0,4x+\dfrac{1}{3}=4\)

\(\left(0,6+0,4+\dfrac{1}{3}\right)x=4\)

\(\dfrac{4}{3}.x=4\)

\(x=4:\dfrac{4}{3}\)

\(x=3\)

{ x² - [ 6² - ( 8² - 9.7)³ - 7.5]³ - 5.3 }³ = 1

{ x² + [ 36 - (64 - 63)³ - 35]³ - 15}³ = 1

[ x² - ( 36 - 1³ - 35 ) - 15 ]³ = 1

[ x² - ( 36 - 1 - 35 ) - 15]³ = 1

[ x² - ( 35 - 35 ) - 15]³ = 1

[ x² - 0 - 15]³ = 1

( x² - 15 )³ = 1

<=> ( x² - 15)³ = 1³

=> x² - 15 = 1

<=> x² = 16

=> x = 4

60%+x+0,4+x+x:3=2

3/5+x+2/5+x+x.1/3=2

(3/5+2/5)+x.(1+1+1/3)=2

1+x.10/3=2

suy ra x.10/3=1

x=1:10/3

x=3/10

vậy x=3/10 nha

60%.x+0,4.x+x:3=2

\(\frac{3}{5}\).x+\(\frac{2}{5}\).x+x:3=2

x.(\(\frac{3}{5}\)+\(\frac{2}{5}\))+x:3=2

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

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

x.\(\frac{4}{3}\)=2

x=2:\(\frac{4}{3}\)

x=\(\frac{3}{2}\)

\(60\%x+0,4x+x:3=2\\ \Leftrightarrow\left(60\%+0,4+\dfrac{1}{3}\right)x=2\\ \Rightarrow\dfrac{4}{3}x=2\\ \Rightarrow x=\dfrac{3}{2}\)

\(60\%x+0,4x+x:3=2\) 

\(x.\left(60\%+0,4+\dfrac{1}{3}\right)=2\) 

                          \(x.\dfrac{4}{3}=2\) 

                              \(x=2:\dfrac{4}{3}\) 

                              \(x=\dfrac{3}{2}\)

\(x^3+3x^2+x+a=x^2\left(x-2\right)+5x\left(x-2\right)+11\left(x-2\right)+22+a=\left(x-2\right)\left(x^2+5x+11\right)+22+a⋮\left(x-2\right)\)

\(\Rightarrow22+a=0\Rightarrow a=-22\)