\(1,\\ a,=12y^2+3y+28-12y^2=3y+28\\ b,=x^2-4x+4-3x^2+9x-x+3=-2x^2+4x+7\\ 2,\\ a,=2x^2y\left(3-2x\right)\\ b,=\left(x+y\right)\left(3-x\right)\\ c,=\left(x-2y\right)^2-z^2=\left(x-2y-z\right)\left(x-2y+z\right)\\ d,=\left(x-y\right)\left(6x^2-x+1\right)\)