Given two real lower Hessenberg matrices

and

of order

and

, respectively, a symmetric matrix of order

is constructed such that whenever

is nonsingular,

and

do not have an eigenvalue in common. When

is singular, its nullity, is the same as the number of common eigenvalues between

and

. A well-known classical result on the relative primeness of two polynomials and the associated Bezoutian matrix is included as a special case.