\documentclass[a4paper,12pt]{article}
\newcommand{\ds}{\displaystyle}
\newcommand{\un}{\underline}
\newcommand{\undb}{\underbrace}
\newcommand{\pl}{\partial}
\parindent=0pt
\begin{document}

{\bf Question}

Find the fixed, or invariant points of the M\"obius transformation

$w=\ds\frac{(2z-5)}{(z+4)}$.


\medskip

{\bf Answer}

We require points $z \stackrel{w=f(z)}{\longrightarrow} z$

Thus $z=\ds\frac{(2z-5)}{(z+4)}$

$\Rightarrow z^2+2z+5=0 \Rightarrow z=-1 \pm 2i$

\end{document}
