1. The problem statement, all variables and given/known data the problem and a possible solution(obtained from a book) is attached as a pdf to the post.However Iam unable to understand it.Please download the attachment. 2. Relevant equations equation no (2) in the pdf.Is there any use of space translation operator in here. 3. The attempt at a solution I have solved this problem using perturbation theory.however Iam intrigued by the method used here.