deletions | additions       diff --git a/Old QFT.tex b/Old QFT.tex  index 8713d75..a4596b6 100644  --- a/Old QFT.tex  +++ b/Old QFT.tex 
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we know that \begin{equation}  [a,a^+]=1=[a,a^+1,1] [a,a^+]=1=[a,a^+,1]  \end{equation}  So trying \begin{equation}  [a,a^+,a]|n>=2n\sqrt{n}|n-1>-(n+1)\sqrt{n}|n-1>-(n-1)\sqrt{n}|n-1>=0  \end{equation}  Meaning \begin{equation}  2aa^+a=aaa^+ + a^+aa  \end{equation}