$\frac{\left(3^2-xy^{-4}\right)^{-2}}{\left(3x^{-2}y^{-2}\right)^{-3}}$

$\frac{1}{x\cdot sin\left(x\right)}-\frac{1}{x\cdot tan\left(x\right)}$

$12+\frac{\left(-6\right)}{-2}$

$12^2+20^2$

$\frac { 2 x ^ { 4 } - 3 x ^ { 2 } + 1 } { x + 2 }$

$\lim_{x\to0}\left(\frac{xe^x}{2^x-1}\right)$

$\frac{d^2}{dx^2}\left(\sqrt{1-x^2}\right)$