a: \(8y^3+27=\left(2y+3\right)\left(4y^2-6y+9\right)\)
b: \(\dfrac{1}{8}x^3-1=\left(\dfrac{1}{2}x-1\right)\left(\dfrac{1}{4}x^2+\dfrac{1}{2}x+1\right)\)
c: \(-x^3-\dfrac{1}{27}=-\left(x^3+\dfrac{1}{27}\right)=-\left(x+\dfrac{1}{3}\right)\left(x^2-\dfrac{1}{3}x+\dfrac{1}{9}\right)\)