deletions | additions       diff --git a/3.tex b/3.tex  index f9ebd79..d72380b 100644  --- a/3.tex  +++ b/3.tex 
...
\begin{equation}  S = \frac{100}{1 + \left(\frac{d}{e\sqrt{\alpha}}\right)^4}  \end{equation} For a city the size of Barcelona, for example, with $\alpha = 0.478$: