- - - Department of Mathematics, Ministry of Education, Thi-Qar, Iraq

In this paper, the invariant subspace method is generalized and improved and is then used together with the Chebyshev polynomial to approximate the solution of the non-linear, mixed fractional partial differential equations FPDEs  with constant, non-constant coefficients. Some examples are given here to illustrate the efficiency of this method.

fractional partial differential equation, Caputo fractional derivative, invariant subspace method, Chebyshev polynomial approximate