$\frac{x^4+8}{x^3+2x-1}$

$\frac{2x^{2}-x^{5}+3}{x^{2}+x+1}$

$\left(1+x^2\right)\frac{dy}{dx}+4xy=\frac{1}{\left(1+x^2\right)^2}$

$-\frac{210}{14}$

$\left(x^4+5\right)\left(x^4-12\right)$

$-3ab\:+\:4ab\:-\:ab\:+\:5ab$

$\lim_{x\to\infty}\left(\frac{x\ln\left(x+1\right)}{x^2+1}\right)$