Si $y = x^2 + \dfrac{1}{x^2 + \dfrac{1}{x^2 + \dfrac{1}{x^2 + \dots \infty}}}$, entonces $\dfrac{dy}{dx}$ es:

1. [a.] $\dfrac{2xy}{2y-x^2}$
2. [b.] $\dfrac{xy}{y+x^2}$
3. [c.] $\dfrac{xy}{y-x^2}$
4. [d.] $\dfrac{2xy}{2 + x^2/y}$