a ) x3 - 2x2 + x
= x3 - x2 - x2 + x
= ( x3 - x2 ) - ( x2 - x )
= x2 . ( x - 1 ) - x . ( x - 1 )
= ( x - 1 )( x2 - x )
b ) x3 - 3x2 - 4x + 12
= ( x3 - 3x2 ) - ( 4x - 12 )
= x2 . ( x - 3 ) - 4 . ( x - 3 )
= ( x - 3 )( x2 - 4 )
= ( x - 3 )( x - 2 )( x + 2 )