$\lim\:_{x\to\:0}\left(\frac{cos\left(x\right)-sen\left(\frac{x}{2}\right)}{x}\right)$

$2x^2-5x+1=0$

$\ln\left(\sqrt{x-2}\right)=3$

$-4a+3a+2a$

$11\sin\left(x\right)+11=0$

$cot^2\left(x\right)+sec^2\left(x\right)=csc^2\left(x\right)$

$\lim_{x\to3}\left(\frac{x-3}{2-\sqrt{x+2}}\right)$