Question

Phân tích đa thức sau thành nhân tử:

(x+2)(x^2-2x)-3x-6

Answer 1

( x + 2 ) ( x² - 2x ) - 3x - 6

= ( x + 2 ) ( x² - 2x ) - ( 3x + 6 )

= ( x + 2 ) ( x² - 2x ) - 3 ( x + 2 )

= ( x + 2 ) ( x² - 2x - 3 )

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

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

= ( x + 2 ) ( x - 3 ) ( x + 1 ) 

Answer 2

( x + 2 )( x² - 2x ) - 3x - 6

= ( x + 2 )( x² - 2x ) - 3( x + 2 )

= ( x + 2 )( x² - 2x - 3 )

= ( x + 2 )[ ( x² - 2x + 1 ) - 4 ]

= ( x + 2 )[ ( x - 1 )² - 2² ]

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

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