$\left(1+z^2\right)\left(1-z^2+z^4\right)$

$\lim\:_{x\to\infty}\left(\frac{3+81^{\frac{221}{x}}}{4}\right)^x$

$\frac{dy}{dx}=\frac{-xy}{\left(x+1\right)}$

$\frac{tanx+coty}{tanx\cdot\:\:coty}+tany+cotx$

$\log13\left(1\right)$

$\left(6\:v\:-4\right)\:\left(2\:v\:+\:5\right)$

$\lim_{x\to\frac{\pi}{2}}\left(\frac{\left(\frac{\pi}{2}-x\right)}{\tan\left(x\right)}\right)$