$\lim_{x\to0}\left(\frac{2x^2}{5x^2+3}\right)$

$336-3430$

$\cos^2\left(\arctan\left(x\right)\right)$

$\lim_{x\to\infty}\left(\sqrt{x^2+2x+3}-\sqrt{x^2-2x+3}\right)$

$\frac{dy}{dx}+\frac{\sqrt{1+y^2}}{\sqrt{1+x^2}}=0$

$\int\frac{\sqrt{49-y^2}}{y}dy$

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