Hoặc
b) 6x−2y9x2−y2.
b) 6x−2y9x2−y2=6x−2y(3x)2−y2=2(3x−y)(3x+y)(3x−y)
=2(3x−y):(3x−y)(3x+y)(3x−y):(3x−y)=23x+y.