For functions like $f(x)=x^n g(x)$ where $g(x)$ is a bounded oscillating function near $x=0$ (like $\sin(1/x)$ or $\cos(1/x)$) and $f(0)=0$: - The function is continuous at $x=0$ if $n>0$. - The function is differentiable at $x=0$ if $n>1$.
If $e^y (x+1) = 1$, then find the value of $$ \frac{d^2 y}{dx^2} - \left(\frac{dy}{dx}\right)^2. $$