$\frac{d}{dx}\left(x\right)=6\cos\left(9x\right)$

$\frac{d}{dx}\left(\frac{x+y}{x-y}=x\right)$

$\frac{d}{dx}\left(2x^2+3y^2-4xy=36\right)$

$\frac{d}{dx}\left(x^2-y^2=25\right)$

$\frac{d}{dx}\left(x-y\right)^3=\left(x+y\right)^2$

$\frac{d}{dx}\left(xy+2x+3x^2=4\right)$

$\frac{d}{dx}\left(\ln\left(xy\right)=e^{xy}\right)$

$\frac{d}{dx}\left(x^{\frac{2}{3}}+y^{\frac{2}{3}}=5\right)$