$a^3+a^2b-7a^2b+9ab^2-4a^3-1ab^2$

$\lim_{x\to0}\left(e^{\frac{1}{x}\ln\:\left(4^{3x+1}\right)}\right)$

$\left(\sqrt{x}-\sqrt{3}\right)^4$

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

$cosx+\frac{senx}{cosx}$

$x^3y'=y^2$

$\csc a-sena\:\cot^2a$