$\lim_{x\to\infty}\left(\frac{\arctan\left(x^6\right)}{x^4}\right)$

$2-7x\le16$

$\frac{\int\left(4x^2+2x+8\right)}{x\left(x^2+8\right)}dx$

$\lim_{x\to\frac{\pi}{2}}\left(\frac{\cos\left(3x\right)}{\cos\left(2x\right)}\right)$

$a4\:\:+1a^2\:\:\:+\:1$

$\left(25a^2+9\right)^2$