$\frac{x-30}{\left(x-5\right)\left(x+6\right)}$

$\lim_{x\to0}\left(\frac{1+sen\left(x-e^x\right)}{\left(arctg\left(x\right)\right)^2}\right)$

$2\cos\:\left(\frac{a}{13}\right)\cos\:\left(\frac{9a}{13}\right)+2\cos\:\left(\frac{4a}{13}\right)\cos\:\left(\frac{a}{13}\right)=0$

$\left(-8\right)-\left(-15\right)+\left(+3\right)-\left(+6\right)$

$\int\left(\cos\left(3x+1\right)\right)dx$

$\sqrt[3]{x^6+y^6}$

$x\sqrt{2x}$