$\displaystyle \begin{array}{{>{\displaystyle}l}} y=\left( x^{2} -1\right)\left( x^{2} -4\right)\left( x^{2} -9\right) =\left( x^{4} -5x^{2} +4\right)\left( x^{2} -9\right)\\ =x^{6} -5x^{4} +4x^{2} -9x^{4} +45x^{2} -36\\ y'=6x^{5} -56x^{3} +98x \end{array}$