$\frac{d}{dx}\left(3xy+5xy^2-7x^4=0\right)$

$\tan\left(80^{\circ}\right)\cdot\cos\left(80^{\circ}\right)\:=\:\sin\left(80^{\circ}\right)$

$\frac{m^{15}-n^{15}}{m^3+n^3}$

$7y\cdot y'=x,7y=9$

$\frac{3y^2+1}{y^3+y}\cdot\:\frac{dy}{dx}=2x$

$6xy\cdot\frac{dy}{dx}-3y^2+3x=0$

$3z^2+18z$