$7\cdot7-4\cdot7$

$\frac{16a^{12}-4b^{14}}{4a^6-2b^7}$

$\frac{d}{dt}\left(8^{\ln\left(5t\right)}\right)$

$\left(3z^2-z\right)^2$

$\lim_{x\to0}\left(\frac{1-\sqrt{1-4\cdot x\cdot b}}{2\cdot x}\right)$

$\lim_{x\to-\infty}\left(\arctan\frac{x^5+1}{x^4+1}\right)$

$sen\theta-tg\theta\:.sen\theta\:=cos\theta\:$