$y=\frac{1}{x}$ হলে $\frac{d x}{d y}$ কোনটি ?

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

$\frac{-1}{\mathrm{y}^{2}}$

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

$\frac{1}{y^{2}}$