x3 - x2 - 4x2 + 8x - 4 = x3 - x2 - 4x2 + 8x - 4
= ( x3 - x2 ) - ( 4x2 - 8x + 4 )
= x2 . ( x - 1 ) - ( 2x - 2 )2
= x2 . ( x - 1 ) - ( 2 . ( x - 1 ) )2
= x2 . ( x - 1 ) - 4 . ( x - 1 )2
= ( x - 1 ) . ( x2 - 4 . ( x - 1 ) )
= ( x - 1 ) . ( x2 - 4x + 4 )
= ( x - 1 ) . ( x - 2 )