$\frac{\left(4x-y\right)^2-\left(4x+y\right)^2}{16xy}$

$\lim_{x\to0}\left(\frac{cos3x-cos9x}{1-cosx}\right)$

$\lim\:_{x\to\:\infty\:}\left(\frac{xe^{2x}-e^{-2x}}{xe^{2x}+e^{-2x}}\right)$

$t=\left(t-8\right)$

$\sqrt[4]{s^{3}\cdot3^{3}}$

$\lim_{x\to0}\left(\frac{x\cdot\left(x+1\right)}{2x^2}\right)$

$1x^2-2x-2$