$2tg^2x+sec^2-2=0$

$\lim_{x\to0}\frac{\cos\left(x\right)-\sin\left(x\right)}{x^2}$

$\lim_{x\to5}\left(\frac{x^2-3x+10}{x^2-25}\right)$

$4\left(x^2+2x\right)-3\left(x-5\right)\ge0$

$\left(3x^4\right)^{-1}$

$x^2-2x-3\ge0$

$\lim_{x\to-2}\left(\frac{8x^3-1}{2x-1}\right)$