$\frac{2sec^2\left(x\right)}{tan\left(2x\right)}$

$\frac{3x^3-2x^2+6x-4}{x-5}$

$e^{x+y}=1$

$\lim_{y\to\infty}\left(ln\left(y-x\right)-ny\left(ln\left(x\right)\right)\right)$

$\frac{81x^8}{9x^4}-\frac{100y^6}{10y^3}$

$-55\cdot65$

$\:\left(-\:2\right)^7+\:\left(-\:3\right)^4+\:\left(-\:4\right)^3\:+\:\left(-\:11\right)^2$