$\lim_{x\to-\infty}\left(\frac{x+1}{x^3-1}\right)$

$\left[\left(-72\right)\:-\:\left(-50\right)\right]\:-\:\left[\left(-39\right)\right]$

$-3\left(w-2\right)$

$-21-\left(-7\right)+4\cdot\left(-7\right)-12\:$

$\lim_{x\to\infty}\left(1+\frac{6}{x}\right)^{\frac{x}{8}}$

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

$8\tan a-\sqrt{54}=0$