\(\dfrac{3x}{3x^3-27x}=\dfrac{3x}{3x\left(x^2-9\right)}=\dfrac{1}{\left(x-3\right)\left(x+3\right)}=\dfrac{x+2}{\left(x-3\right)\left(x+3\right)\left(x+2\right)}\\ \dfrac{x+1}{\left(x+2\right)\left(x+3\right)}=\dfrac{\left(x+1\right)\left(x-3\right)}{\left(x-3\right)\left(x+3\right)\left(x+2\right)}\)