$\lim_{x\to\infty}\left(\frac{\left(2x-1\right)\left(3x+1\right)}{x^3+1}\right)$

$x=\left(x^2+1\right)\cdot\left(\tan\left(y\right)\right)\cdot y'$

$6a^3b-2ab^3$

$\lim_{x\to r}\left(\frac{r^5-x^5}{r^3-x^3}\right)$

$\frac{8x^4+4x^3+6x^2}{2x^2+1}$

$-30=\frac{x}{3}$

$2x+7\:+2x$