$\lim_{x\to0}\left(\frac{-5x^2-\frac{1}{12}x^4}{x^2}\right)$

$30xy-20^3+40y^2$

$\lim_{x\to2}\left(x^2+\frac{1}{9}\right)\left(x-\frac{1}{3}\right)$

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

$\lim_{x\to-2.5}\frac{\tan\left(x+3\right)}{x+3}$

$-x^2dy=-dx$

$\int\left(r^2e^{-3r}\right)dr$