The book I am using is "Digital Signal Processing" (Third Edition) by Prokis and Manolakis. It is question 2-45 on page 144.
Consider the system described by the difference equation:
determine b in terms of a so that
THE SUMMATION OF h(n)=1
The limits of the summation are n=- infinity to
n=infinity (I used the term summation instead of the
the mathematical symbol.)
The solution is in an attachment as a step-by-step equational process.