# Annihilation and Creation operator problem

I've looked through all my course notes, but I just don't even know where to start with this problem.

The problem:

$$\langle 1 \mid x^2 \mid 2 \rangle$$

Use the annihilation and creation form for x to obtain the above matrix element.

What I do know:

I know that $$x = \sqrt{\hbar / 2mw}(a^\dagger + a)$$

But where do I go from here? Any help or pointers are much appreciated!

## Answers and Replies

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