On Stability of Multi Fractional Order Differential Equations with Constant Coefficient

         The use of fractional orders differential and integral operators in mathematical models has been increasingly widespread in recent years. The non-linear multi-term fractional (arbitrary) order differential equation has been considered. Its solution existences and uniqueness are proved by transform it into a linear system of equations. Also, stability theorem for such a differential equation is presented (by transform it into an ordinary differential equations, as well as, different examples, are presented to verify our stability results.