$\sec^2\left(x\right)\frac{dy}{dx}+\:\csc\left(y\right)\:=0$

$2x-6=x-14$

$\frac{x+3}{x\left(x^2+9\right)}$

$\:ydx-2\left(\:x+y\right)dy=0\:\:$

$\lim\:_{x\to\:-\infty\:}\:\left(x\left(2cos\left(\frac{1}{x}\right)-2\right)\right)$

$\sqrt{2^2-x^2}$

$25a^2-5\left(5a\right)$