If $g$ is differentiable, the Reciprocal Rule says that $$\frac{d}{dx} \left[ \frac{1}{g(x)} \right] = - \frac{g'(x)}{g(x)^2},$$ provided $g(x) \ne 0$. Use the Reciprocal Rule to differentiate $$y = \frac{1}{8x^{4}+9x^{2}+5}.$$

$\displaystyle \frac{dy}{dx} =$