$\left(x-2\right)+\left(x+1\right)$

$\:3^x+3^{x+2}+3^{x+3}=999$

$\lim_{x\to-\infty}\left(\frac{\left(2-x^3\right)}{\left(x^2+x\right)}\right)^3$

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

$\frac{36x^2}{2}$

$\left(\frac{3}{4}a^2b\cdot\:\frac{1}{3}ab^3\right)$