$xy'+x-xy^3=0$

$y=ln\left(x\cdot cos\left(x\right)\right)+5^{-x}$

$\lim_{x\to\frac{\pi}{2}}\left(\frac{2\cos^2\:x+cosx-1}{2\cos^2-3cos+1}\right)$

$\frac{d}{dy}\frac{x+y}{xy}=x$

$16\left(12\right)+31$

$\left(x^4+3x^2-\frac{1}{2}x+2\right)\cdot\left(-\frac{1}{3}\right)$

$14-\left|-4+12\right|-6x$