Ok, I think I got it,
so using:
e1 = \frac{1}{\sqrt{2}}(|+,-> + |-,+>) with eigenvalue 2hbar^2
and
e2 = \frac{1}{\sqrt{2}}(|+,-> - |-,+>) with eigenvalue 0
I rewrite: |+,-> as (e1 + e2)*(sqrt(2)/2) and |-,+> as (e1 - e2)*(sqrt(2)/2)
Combine e1 and e2 terms. And then the...