$\lim_{x\to\infty}\left(\tan\left(\frac{\pi x}{2x+1}\right)\right)^{\frac{1}{x}}$

$\sqrt{\left(x-1\right)\cdot\left(x+5\right)}$

$\frac{x^3-26x-41}{x+4}$

$x^4+625+x^4$

$\left(3x^2+2x+3\right)\arctan\left(x\right)$

$\frac{dy}{dx}=x\left(e^{-y}\right)\left(\ln\left(x\right)\right)$

$xydx-\left(x+2\right)^2dy=0$