$\int a^2\sqrt{a^3+3}da$

$13\cdot10^5$

$\lim_{x\to0}\left(1-sqrt\left(x^2+x\right)\right)$

$\frac{40}{\frac{\:5}{6}}$

$\int_{\frac{\pi}{3}}^{\frac{\pi}{2}}\left(sec^2\left(3x\right)\right)dx$

$\frac{14}{2\sqrt{7}}$

$\int_{-2}^0\left(\frac{r^3}{\sqrt{4+r^2}}\right)dx$