1. The problem statement, all variables and given/known data 2. Relevant equations This is the problem that I am trying to solve. 3. The attempt at a solution https://docs.google.com/file/d/0B0Wxm870SWTNV0xjdmVRc09TTm8/edit The approach of solving this problem is to first convert the two systems' state space representations into s-domain, combine them, then finally convert the final result back to the frequency domain. I am stuck; I can find the output, y, but I don't know how do I derive the state representation from the output. Is my approach correct? or do I need to use another approach? Any suggestion will be appreciated; thank you in advance!!