we have the following:
[tex]y=\frac{1}{(x^2-1)(x^2+5x+2)}[/tex]derivate:
[tex]\begin{gathered} y^{\prime}=\frac{\frac{d}{dx}\lbrack(x^2-1)\rbrack\cdot(x^2+5x+2)+\frac{d}{dx}\lbrack(x^2+5x+2)\rbrack(x^2-1)}{(x^2-1)^2(x^2+5x+2)^2} \\ y´=\frac{2x\cdot(x^2+5x+2)+(2x+5)\cdot(x^2-1)}{(x^2-1)^2(x^2+5x+2)^2} \\ y^{\prime}=\frac{2x^3+10x^2+4x+2x^3-2x+5x^2-5}{(x^2-1)^2(x^2+5x+2)^2} \\ y^{\prime}=\frac{4x^3+15x^2+2x-5}{(x^2-1)^2(x^2+5x+2)^2} \end{gathered}[/tex]