$\left(x+\sqrt{-4}\right)^4+\left(x-\sqrt{-4}\right)^4$

$\frac{\cos\left(-x\right)}{1-sin\left(-x\right)}=secx-tanx$

$\frac{x-4}{\sqrt{x}}=0$

$\lim_{x\to-3}\left(\frac{x^2+5x+6}{x+4}\right)$

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

$\log_c\left(x\right)+\log_c\left(y\right)$

$2=\sqrt{13-3y}$