$-6^{19}-6^8$

$8x^3\:-\:64$

$\left(xy+y\right)\left(xy-x\right)$

$\int e^{\frac{75}{4}t}\cdot\cos\left(2t\right)dt$

$\frac{1}{\cos\left(x\right)}-\frac{\cos\left(x\right)}{1+\sin\left(x\right)}=\frac{1}{\cos^2x}$

$\lim_{x\to0}\left(ax\right)\tan\left(bx\right)$

$x-\frac{\frac{1}{x}}{\frac{1}{x^2}}$