$$-21-\:15g$$

$$6x^2+30x+36$$

$$cos\left(\frac{\pi}{6}-x\right)=\frac{1}{2}\left(\sqrt{3}cosx+sinx\right)$$

$$3^25^8$$

$$\left(a-6a^2-2a^3+10\right)\cdot2a$$

$$\lim_{x\to\infty}\left(-\frac{x-x^2}{5}\right)$$