- #1

izzmach

- 7

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*a*be a lowering operator and

*a†*be a raising operator.

Prove that

*a((a†)^n)*=

*n (a†)^(n-1)*

Professor suggested to use induction method with formula:

*((a†)(a) + [a,a†]) (a†)^(n-1)*

But before start applying induction method, I would like to know where the given formula comes from. Someone please explain it briefly? Thank you.