$\frac{a^2-2a-3}{a+3}$

$x'=x\cdot t$

$\frac{\cos\left(x\right)+\sin\left(x\right)\cdot\tan\left(x\right)}{\sin\left(x\right)\cdot\sin\left(x\right)}$

$\left(3-x^2\right)\left(2x+1\right)^4$

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

$\lim_{x\to0}\left(\frac{\arcsin\left(x^2\right)}{x^2}\right)$

$\lim_{x\to0}\left(\left(5x+cosx\right)^{\frac{1}{x}}\right)$