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

$\left(7x-6\right)\left(x^2-5x-1\right)$

$\frac{d}{dx}\frac{3x-\:1}{x^2\:+\:3\:}^2$

$\frac{dy}{dx}-2x-\frac{1}{x}=0$

$\int_{-1}^3\left(\frac{x}{2-x}\right)dx$

$12\left(13+11+8\right)$

$\lim_{x\to2}\left(\frac{\sqrt{x-2}}{\sqrt{x^{2}-4}}\right)$