Can someone explain to me how(adsbygoogle = window.adsbygoogle || []).push({});

[itex]H(\sum_n w_n |a_n><a_n|) = \sum_n w_n(H|a_n><a_n|-|a_n><a_n|H)[/itex]

I've done this before and I remember being confused about it before then finding out it was something simple.. I should really start filing my notes away for such an eventuality

I can't seem to work out what the next step is at all.

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# Basic Operator question

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