\(P=3x^2+6x+2x+4=3x\left(x+2\right)+2\left(x+2\right)=\left(x+2\right)\left(3x+2\right)\\ P=3\left(x^2+2\cdot\dfrac{4}{3}x+\dfrac{16}{9}\right)-\dfrac{4}{3}\\ P=3\left[\left(x+\dfrac{4}{3}\right)^2-\dfrac{9}{4}\right]=3\left(x+\dfrac{4}{3}-\dfrac{3}{2}\right)\left(x+\dfrac{4}{3}+\dfrac{3}{2}\right)\\ P=3\left(x-\dfrac{1}{6}\right)\left(x+\dfrac{17}{6}\right)\)