Hoặc
Tính: x6−y6x4−y4−x3y+xy3.
Ta có: x6−y6x4−y4−x3y+xy3
=x32−y32x3x−y+y3x−y
=x3+y3x3−y3x3+y3x−y
=x3−y3x−y
Vậy x6−y6x4−y4−x3y+xy3=x2+xy+y2.