$\left(x+y\right)dx+xdy=0\:$

$3x^2=108$

$\sqrt{\frac{1-x^2}{1+x^2}}$

$\left(\frac{2}{3}x-\frac{5}{6}\right).\left(\frac{2}{3}x+\frac{5}{6}\right)$

$2\pi\int_1^{\infty}\left(\frac{1}{x}\sqrt{1+\frac{1}{x^4}}\right)dx$

$\int x\sqrt{12-x^2}dx$

$ln\left(\frac{1+x}{1-x}\right)$