...

<=> 3x^5(x-3) - 4x^4(x-3) + 7x^3(x-3) - 5x^2(x-3) + 4x(x-3) - (x-3) = 0 

<=> (x-3)(3x^5 - 4x^4 + 7x^3 - 5x^2 + 4x - 1) = 0 

<=> (x-3)[3x^4(x-1/3) - 3x^3(x-1/3) + 6x^2(x-1/3) - 3x(x-1/3) + 3(x-1/3)] = 0 

<=> (x-3)(x-1/3)(3x^4 - 3x^3 + 6x^2 - 3x + 3) = 0 

<=> (x-3)(x-1/3)[3(x^4+2x^2+1) - 3x(x^2+1)] = 0 

<=> (x-3)(x-1/3)(x^2+1)[3(x^2+1) - 3x]  = 0 

<=> 3(x-3)(x-1/3)(x^2+1)(x^2+1-x) = 0 

.... 

cu dương to không

a) 6x³ + 3x² + 4x + 2

= ( 6x³ + 3x² ) + ( 4x + 2 )

= 3x²( 2x + 1 ) + 2( 2x + 1 )

= ( 2x + 1 )( 3x² + 2 )

=> (  6x³ + 3x² + 4x + 2 ) : ( 3x² + 2 ) = 2x + 1

b) 2x³ - 26x - 24

= 2( x³ - 13x - 12 )

= 2( x³ + 4x² - 4x² + 3x - 16x - 12 )

= 2[ ( x³ + 4x² + 3x ) - ( 4x² + 16x + 12 ) ]

= 2[ x( x² + 4x + 3 ) - 4( x² + 4x + 3 ) ]

= 2( x² + 4x + 3 )( x - 4 )

=> ( 2x³ - 26x - 24 ) : ( x² + 4x + 3 ) = 2( x - 4 ) = 2x - 8

c) x³ - 7x + 6 

= x³ - 3x² + 3x² + 2x - 9x - 6

= ( x³ - 3x² + 2x ) + ( 3x² - 9x + 6 )

= x( x² - 3x + 2 ) + 3( x² - 3x + 2 )

= ( x² - 3x + 2 )( x + 3 )

=> ( x³ - 7x + 6 ) : ( x + 3 ) = x² - 3x + 2

a,\(\left(6x^3+3x^2+4x+2\right)\div\left(3x^2+2\right)\)

\(=\left[3x^2\left(2x+1\right)+2\left(2x+1\right)\right]\div\left(3x^2+2\right)\)

\(=\left[\left(3x^2+2\right)\left(2x+1\right)\right]\div\left(3x^2+2\right)\)

\(=2x+1\)