Ta có : x3 + 27 + (x + 3) (x - 9)
= (x + 3)(x2 - 3x + 9) + (x + 3) (x - 9)
= (x + 3) (x2 - 4x)
= (x + 3) x(x - 4)
Nước kia mình đi sai , cho mình đi lại nha :>
x3 + 27 + ( x + 3 )( x - 9 )
= x3 + 33 + ( x + 3 )( x - 9 )
= ( x + 3 )( x2 - 3x + 9 ) + ( x + 3 )( x - 9 )
= ( x + 3 )( x2 - 3x + 9 + x - 9 )
= ( x + 3 )( x2 - 2x )
= ( x + 3 )x( x - 2 )