$\frac{d}{dx}\left(x+\cos\left(x+y\right)\right)=0$

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

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

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

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

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

$\frac{d}{dx}\left(tan^{9-7x}\left(x\right)\right)$

$\frac{d}{dx}\left(x^2+y^2=16\right)$