Stabilita RK metod

{expx1,expx2,expx3,expx4} =Normal@(Series[ Exp[ x],{x,0,rad}]/.{{rad->1},{rad->2},{rad->3},{rad->4}})
Abs[%]/.x->u+I v;
Show[ Table[ ContourPlot[%[[k]],{u,-3,1},{v,-3,3},Contours->{1},ContourShading->None,Axes->True,ContourStyle->Hue[k/5]],{k,1,4}]]