(d^2 x)/(d y^2) equals

Since, \begin{aligned} \Rightarrow \quad \frac{d}{d y}\left(\frac{d x}{d y}\right) & =\frac{d}{d x}\left(\frac{d y}{d x}\right)^{-1} \frac{d x}{d y} \\ \frac{d^2 x}{d y^2} & =-\left(\frac{d^2 y}{d x^2}\right)\left(\frac{d y}{d x}\right)^{-2}\left(\frac{d x}{d y}\right) \\ & =-\left(\frac{d^2 y}{d x^2}\right)\left(\frac{d y}{d x}\right)^{-3} \end{aligned}