Alright, the question is:

transform $\displaystyle 2x\frac{d^2x}{dt^2} -6(\frac{dx}{dt})^2=x^2-3x^4$

into $\displaystyle \frac{d^2y}{dt^2}+y=3$ by using the substitution $\displaystyle y=\frac{1}{x^2}$

I'm stuck on differentiatin twice

Help, please?