$\frac{\frac{6}{a-4}+2}{2-\frac{4}{a-4}}$

$6b^2+17b+5$

$\left(x^{-3}\cdot y^2\right)^4$

$4.9\infty-5$

$\int ln\left(ex\right)dx$

$\left(6u^4+39u^3-18u^2\right)\left(-u\right)$

$\lim_{x\to-\left(\infty\right)}\left(\frac{\left(e^x\left(x^2+4\right)\right)}{x-2}\right)$