$y=\tan ^{-1} \frac{2 x}{1-x^{2}}$ হলে $\frac{d y}{d x}=$ কত ?

$\frac{-2}{1+x^{2}}$

$\frac{2}{1+x^{2}}$

$\frac{1}{1+4 x^{2}}$

$\frac{4}{1+x^{2}}$