$\frac{81x^2-16m^2}{9x+4m}$

$\frac{dy}{dx}=\frac{x\left(y^3+y\right)}{3y^2+1}$

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

$\arccos\left(x\right)=\arctan\left(\sqrt{\frac{1-x^2}{x}}\right)$

$\lim_{x\to\infty}\:\frac{-2^n}{-2^n}$

$\frac{dy}{dx}=\frac{x^2-3}{y^2},\:y\left(0\right)=4$

$e^y\:y^'=\left(4x^2+2x-3\right)$