PROOF. Similarly as in the proof of Theorem 2.3 above, a sufficient,
though not necessary, condition that the matrices R and A be similar is,
of course, that A and B have no common characteristic root. In this case
a solution of (1.1) not only exists, but is unique. But this is also necessary
for the hypothesis here implies thatfp(A)=O, whencefg(A) is a multiple
of the minimum polynomial of A and that M=fp(B) is nonsingular,
whencefp(A) cannot vanish for any characteristic root of B.
The matrices of fp(R) and R commute which implies the following
identities: