$$20^{-10}\cdot20^{11}$$

$$-cot\left(x\right)-1=0$$

$$16x^3-5x^4$$

$$\left(4x^3\right)^2\:$$

$$\lim_{x\to2}\left(\frac{x^2+1x+2}{x^2-4}\right)$$

$$\left(\frac{bh}{2}-\frac{4hb^3}{24b^2}\right)^{-\frac{b}{2}}$$

$$\lim_{x\to0}\left(\frac{3}{x}\right)^{3x}$$