$5\left(2-u\right)-u=2\left(u+1\right)$

$\lim_{x\to\infty}\left(\frac{\pi^x}{e^x+\pi^x}\right)$

$\int\frac{0.4e^{-0.1x}}{\left(1+e^{-0.1x}\right)^2}dx$

$\int\frac{2}{\left(x-1\right)\left(x+1\right)}dx$

$\sqrt{26^2-23^2}$

$28\left(\frac{1}{4}z^8-\frac{1}{14}\right)\left(\frac{1}{4}z^8+\frac{1}{14}\right)$

$\left(3x+5\right)\left(7x-4\right)$