1. The problem statement, all variables and given/known data See question 5 2. Relevant equations 3. The attempt at a solution For part a, it is very easy. Multiply the inverse of A 2 times on both side, we can see the B=inverse of A. i.e. The required B is inverse of A, then the proof is finished. But how about part b? It seems it is the same part a. Is part b also correct?