$\lim_{x\to3}\left(\frac{x^2-9}{-5x^2+5x+3}\right)$

$x^2-4x+13$

$\left(\frac{\left(\sin\left(x\right)+\cos\left(x\right)^2\right)}{\cos\left(x\right)}\right)\cot\left(x\right)$

$phi''\left[n\right]\:+\:2\:n\cdot phi'\left[n\right]\:==\:0$

$x^2-40x$

$\frac{dy}{dx}\left(y=\left(e^{-2x}\right)\sqrt[3]{x^2-1}\sqrt{1+\sqrt{x}}\right)$

$\frac{dy}{dx}+xe^x=0$