1) The differential equation of the rectangular hyperbola, where axes are the asymptotes of the hyperbola, is A) $y \frac{dy}{dx}=x$ B) $x \frac{dy}{dx}=-y$ C) $x \frac{dy}{dx}=y$ D) $x dy+ydx=c$ Answer: Option BExplanation: The differential equation of the rectangular hyperbola $xy=c^{2}$ is $y+x \frac{dy}{dx}=0$ $\Rightarrow$ $x \frac{dy}{dx}=-y$
