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

$\frac{2}{5}\:.\:\left(10\right)$

$y'\:=\:6x\:-\:xy\:-\:y\:+\:6$

$\frac{d}{dx}x^3y^2=a$

$\left(8\:+\:x\right)\left(8\:-\:x\right)$

$f\left(x\right)=\sqrt{\left(6-x\right)^2}+\sqrt{x-6}$

$\frac{dx}{dy}=\frac{x\left(ln\left(x\right)\right)}{y}$