\(=3y^2-3\left(x^2-4x+4\right)=3y^2-3\left(x-2\right)^2\)
\(=3\left[y^2-\left(x-2\right)^2\right]=3\left(y-x+2\right)\left(y+x-2\right)\)
\(-3x^2+12x-12+3y^2\\= 3y^2+\left(-3x^2+12x-12\right)\\ =3y^2-3\left(x^2-12x+12\right)\\ =3y^2-3\left(x-2\right)^2\\ =3\left[y^2-\left(x-2\right)^2\right]\\= 3\left[y-\left(x-2\right)\right]\left[y+\left(x-2\right)\right]\\= 3\left(y-x+2\right)\left(y+x-2\right)\)