$\lim_{u\to0}\left(\frac{\left(x+u\right)^2-u}{u}\right)$

$\lim_{x\to-3}\left(\frac{x^2+5x+6}{\:x^2+9}\right)$

$\left(\left(c^2+4d^2\right)-c^2d^2\right)$

$\tan\left(\frac{\pi}{6}-\frac{3\pi}{4}\right)$

$\lim_{x\to0}\left(x\:cotx\right)$

$\int\frac{cos\left(x\right)^2}{sin\left(x\right)}dx$

$25x^{4}+100x^{2}y^{3}+100$