$-9b^2+27b^2$

$\frac{y^9z^4}{\left(y^{-1}z\right)^5}$

$\frac{x^3+5}{x^2-1}$

$\frac{dy}{dx}=\frac{\sin\left(x\right)\cos\left(y\right)}{\cos\left(x\right)\sin\left(y\right)}$

$\lim\:_{x\to\:\:1}\left(\frac{\sqrt{x-1}}{x-1}\right)$

$\left(9-a^2\right)^2$

$\lim_{x\to4}\left(\frac{\:ln\left(x\right)}{\left(x-1\right)^2}\right)$