1. ... Expand the Eigenvalue as a power series in epsilon, up to second order: λ=[3+√(1+4 ε^2)]V0 / 2 2. Relevant equations I am familiar with power series, but I don't know how to expand this as one. 3. The attempt at a solution: I have played around with the idea of using known power series of functions such as e^x, yet I haven't found a way to make that useful.