` color{#e6f0ff}{@}color{#c7ddff}{T}color{#99c2ff}{o}color{#66a3ff}{r}color{#3385ff}{a}color{#0066ff}{U}color{#0044cc}{F}color{#002d80}{O}color{#001b4d}{@} `

Bài ` 4 : `

` x^4 - 2x^3 - 3x^2 + 8x - 4 `

` = ( x^4 - 2x^3 ) - ( 3x^2 - 6x ) + ( 2x - 4 ) `

` = x^3 ( x - 2 ) - 3x ( x - 2 ) + 2 ( x - 2 ) `

` = ( x - 2 ) ( x^3 - 3x + 2 ) `

` = ( x - 2 ) ( x^3 - x - 2x + 2 ) `

` = ( x - 2 ) [ x ( x^2 - 1 ) - 2 ( x - 1 ) ] `

` = ( x - 2 ) [ x ( x - 1 ) ( x + 1 ) - 2 ( x - 1 ) ] `

` = ( x - 2 ) { ( x - 1 ) [ x ( x + 1 ) - 2 ] } `

` = ( x - 2 ) [ ( x - 1 ) ( x^2 + x - 2 ) ] `

` = ( x - 2 ) { ( x - 1 ) [ x ( x - 1 ) + 2 ( x - 1 ) ] } `

` = ( x - 2 ) [ ( x - 1 )^2 ( x + 2 ) ] `

` = ( x - 1 )^2 ( x - 2 ) ( x + 2 ) `

` Bài ` 5 : `

` x^4 - 5x^3 + 5x^2 + 5x - 6 `

` = ( x - 4 - x^3 ) - ( 4x^3 - 4x^2 ) + ( x^2 - x ) + ( 6x - 6 ) `

` = x^3 ( x - 1 ) - 4x^2 ( x - 1 ) + x ( x - 1 ) + 6 ( x - 1 ) `

` = ( x - 1 ) ( x^3 - 4x^2 + x + 6 ) `

` = ( x - 1 ) [ ( x^3 + x^2 ) - ( 5x^2 + 5x ) + (  6x + 6 ) ] `

` = ( x - 1 ) [ x^2 ( x + 1 ) - 5x ( x + 1 ) + 6 ( x + 1 ) ] `

` = ( x - 1 ) [ ( x + 1 ) ( x^2 - 5x + 6 ) ] `

` = ( x - 1 ) [ ( x + 1 ) ( x^2 - 2x - 3x + 6 ) ] `

` = ( x - 1 ) { ( x + 1 ) [ x ( x - 2 ) - 3 ( x - 2 ) ] } `

` = ( x - 1 ) { ( x + 1 ) [ ( x - 2 ) ( x - 3 ) ] } `

` = ( x - 1 ) ( x + 1 ) ( x - 2 ) ( x - 3 ) `

Bài ` 6 : `

` x^4 + 2x^3 - 13x^2 - 14x + 24 `

` = ( x^4 - x^3 ) + ( 3x^3 - 3x^2 ) - ( 10x^2 - 10x ) - ( 24x - 24 ) `

` = x^3 ( x - 1 ) + 3x^2 ( x - 1 ) - 10x ( x - 1 ) - 24 ( x - 1 ) `

` = ( x - 1 ) ( x^3 + 3x^2 - 10x - 24 ) `

` = ( x - 1 ) [ ( x^3 - 3x^2 ) + ( 6x^2 - 18x ) + ( 8x - 24 ) ] `

` = ( x - 1 ) [ x^2 ( x - 3 ) + 6x ( x - 3 ) + 8 ( x - 3 ) ] `

` = ( x - 1 ) [ ( x - 3 ) ( x^2 + 6x + 8 ) ] `

` = ( x - 1 ) [ ( x - 3 ) ( x^2 + 2x + 4x + 8 ) ] `

` = ( x - 1 ) { ( x - 3 ) [ x ( x + 2 ) + 4 ( x + 2 ) ] } `

` = ( x - 1 ) [ ( x - 3 ) ( x + 2 ) ( x + 4 ) ] `

` = ( x - 1 ) ( x - 3 ) ( x + 2 ) ( x + 4 ) `