\(a,=4\left(x+3\right)-x\left(x+3\right)\\ =\left(4-x\right)\left(x+3\right)\\------\\ b,=\left(x^3-27\right)-4x\left(x-3\right)\\ =\left(x-3\right)\left(x^2+3x+9\right)-4x\left(x-3\right)\\ =\left(x-3\right)\left(x^2+3x+9-4x\right)\\ =\left(x-3\right)\left(x^2-x+9\right)\)