A note on solutions of the matrix equation AXB=C

This paper deals with necessary and sufficient condition for consistency of the matrix equation $AXB = C$. We will be concerned with the minimal number of free parameters in Penroses formula $X = A^(1)CB^(1) + Y - A^(1)AYBB^(1)$ for obtaining the general solution of the matrix equation and we will establish the relation between the minimal number of free parameters and the ranks of the matrices A and B. The solution is described in the terms of Rohdes general form of the {1}-inverse of the matrices A and B. We will also use Kronecker product to transform the matrix equation $AXB = C$ into the linear system $(B^T otimes A)vecX = vec C$.

The Compositions of the Differential Operations and Gateaux Directional Derivative

In this paper we determine the number of the meaningful compositions of higher order of the differential operations and Gateaux directional derivative.