Find $\displaystyle \frac{d^2y}{dx^2}$ by implicit differentiation: $\displaystyle 2x^3-3y^2=8$

So far I get

$\displaystyle \frac{dy}{dx}=\frac{x^2}{y}$

$\displaystyle \frac{d^2y}{dx^2}=\frac{2y}{x}$ <----- incorrect

correct answer= $\displaystyle \frac{2xy^2-x^4}{y^3}$

How do i find the correct answer?