$$4\cdot\left(-3-5\right)\:$$

$$\lim_{x\to0}\left(\left(\frac{\left(2^x+6^x\right)}{x}\right)\right)$$

$$1.728+11$$

$$\left(\frac{2}{5}ab-\frac{1}{2}a^3\right)^2$$

$$4x^2-26x+169$$

$$\left(a^3\:-\:2a^2\right)\:\left(3a^2\:-\:4a^3\right)$$

$$\lim_{x\to0}\frac{x^2+7}{x}$$