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**The problem:**

[tex] \langle 1 \mid x^2 \mid 2 \rangle [/tex]

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

**What I do know:**

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

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