deletions | additions       diff --git a/p7.tex b/p7.tex  index b26cfee..46ea961 100644  --- a/p7.tex  +++ b/p7.tex 
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$x^2 = 1modn$  $x^2 = 1modn$ 1modn  \Rightarrow \frac{x^2-a}{n} \Rightarrow $n n  | (x-1)(x+1)$ So $(x-1) = np$ or $(x+1) = np$; \Rightarrow $x = np\pm1$  \end{itemize}