Copyright © 2012 Fang Wang et al. This is an open access article distributed under the   Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
        
     
Abstract
The main purpose of this paper is to obtain the unique solution of the constant coefficient homogeneous linear fractional differential equations  and the constant coefficient nonhomogeneous linear fractional differential equations  if  is a diagonal matrix and  and prove the existence and uniqueness of these two kinds of equations for any  and . Then we give two examples to demonstrate the main results.