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

$4\left(3a-5b-7\right)$

$-4\left(3n-5\right)-7n$

$z=senx\cdot cosy,\:x=\sqrt{t},\:y=\frac{1}{t}$

$x^2\:+\:26x\:+\:169$

$\log\left(\frac{x\left(x+7\right)}{\left(x+5\right)^8}\right)$

$\frac{d}{dx}3x^3+9xy^2=7x^3$