$\lim_{x\to-\sqrt{13}}\left(\frac{x^2-13}{\sqrt{x^2+3}-4}\right)$

$\left(b^4-3\right)^3$

$\left(-5a-2b-36\right)\left(7a-3b+5c\right)\left(-8a+5b-3c\right)$

$\frac{tgx+tgx+ctgx}{tgx-tgx+ctg}$

$cos\left(\frac{\pi}{5}\right).\cos\left(\frac{\pi}{5}\right)$

$x\left(28+7x\right)=0$

$\:\left(sen2x\:+\:2senx\right)\left(1-\cos\left(x\right)\right)$