In[1]:= eqtn = r'@tD == - 0.1 * r@tD; gensol = DSolve@eqtn, r@tD,tD; parsol = DSolve@8eqtn, r@0D 200<,r@tD,tD; greqtn = r@tD. parsol; Plot@Evaluate@greqtnD, 8t, 0, 20<, PlotLegends fi "Expressions", PlotRange fi 80, 200<, PlotLabel fi "Decay Model", GridLines fi 883<, 8<<, AxesLabel fi 8"Time", "Radioactive material in Grams"<D grval = greqtn .t fi 3 Out[5]= 0 5 10 15 20 Time 50 100 150 200 Radioactive material in Grams Decay Model 200. ª -0.1 t Out[6]= 8148.164<