$3\left(-\frac{1}{x}\right)$

$\frac{x}{\sqrt{16+4x^2}}$

$\lim_{x\to0}\left(\frac{x^2-1-\ln\left(x\right)}{\left(\ln\left(x\right)\right)\cdot\left(x^2-1\right)}\right)$

$-x^2-4x-1$

$\left(mn\right)^3$

$\int_{-\infty}^{-2}\left(\frac{1}{x}\right)dx$

$\lim_{x\to25}\left(\frac{1}{5-x^{\frac{1}{2}}}\right)$