$\frac{-400}{-25}$

$-2\left(3x\:-\:4\right)=\:20$

$\lim_{x\to1}\left(\left(x-1\right)\cdot\frac{cos\left(x\right)}{x^3-17x^2+80x-64}\right)$

$-\left|-64\right|$

$x^5-x^2$

$\frac{d}{dx}\left(a^3bxy^3+2aby=\ln\left(\frac{ax^2}{by^3}\right)\right)$

$\left(6a\:+\:5b\right)\:\left(6a\:-\:5b\right)$