$\int x^2\sqrt{16+x^2}dx$

$\log\left(x+3\right)+\log\left(x-5\right)=\log\left(x-6\right)$

$4x^2y+6yx^2$

$\frac{\left(\tan x+1\right)\left(\tan x-1\right)-\sec^2x}{\tan x}$

$\frac{dy}{dx}=\frac{2x+y-1}{-\left(6x+3y+1\right)}$

$\frac{dy}{dx}y^2-9x=3$