An asymptotic equation is derived which describes the far-field behavior of the governing system of partial differential equations for a one dimensional unsteady plane and radially symmetric flow of an \ninviscid non-ideal relaxing gas; this evolution equation, is a generalized Burger’s equation, which enables us to study in detail the various effects that appear in the propagation of plane, cylindrical and spherical waves in a dissipative medium with a quadratic nonlinearity. An approximate solution of \nthis equation is obtained by using the Homotopy Analysis method (HAM); The HAM enables us to determine the various effects of nonlinearity, relaxation and geometrical spreading.