3x^2-6xm-9m^2=
=4х^2 - (x^2 + 6mx + 9m^2)=
=4x^2 - (x + 3m)^2=
=(2x-x-3m)(2x+x+3m)=
=(x-3m)(3x+3m)=
3(x-3m)(x+m)
3x^2-6xm-9m^2=
=4х^2 - (x^2 + 6mx + 9m^2)=
=4x^2 - (x + 3m)^2=
=(2x-x-3m)(2x+x+3m)=
=(x-3m)(3x+3m)=
3(x-3m)(x+m)