\(9x^4-12x^5+4x^6=4x^4\left(\dfrac{9}{4}-3x+x^2\right)=\left(2x\right)^2\left(\dfrac{3}{2}-x\right)^2=\left[2x-\left(\dfrac{3}{2}-x\right)\right]\left(2x+\dfrac{3}{2}-x\right)\)\(=\left(2x-\dfrac{3}{2}+x\right)\left(2x+\dfrac{3}{2}-x\right)=\left(3x-\dfrac{3}{2}\right)\left(x+\dfrac{3}{2}\right)\)