$-62\ge31u$

$\left(2x+y\right)^2-\:\left(2x-y\right)^2$

$\left(7-7x\right)^2$

$\lim_{x\to\frac{\pi}{2}}\left(x-\frac{\pi}{2}\right)\cdot\sec\left(x\right)$

$4sinxcos2x+4cosxsin2x-1=0$

$\lim_{x\to\infty}\left(sin\left(x\right)ln\left(4x\right)\right)$

$\lim_{x\to2}\left(\frac{1-\cos\left(\sqrt{x-2}\right)}{\left(x-2\right)^{\frac{2}{3}}}\right)$