$6x+x^2=31$

$\left(-\:3a^2\:+\:2ab\:+\:2b^2\right)+\left(2ab\:-\:7a^2\:-\:5b^2\right)$

$f\left(x\right)=\frac{\left(x^{-2}-x^3\right)}{e^{5x}}$

$\left(13m+5n\right)^3$

$yx^3-3yx$

$2.75+\left(-2\right)+\left(-5.25\right)$

$\lim_{x\to\infty}\left[x-ln\left(x^2+1\right)\right]$