Figure explanation (see also comments in the script)

The figure above shows three curves plotted in the same figure window.

The blue curve y1 is the plot of the rational function

The above formula estimates exp(-x) for small values of x.

The red curve y2 is the plot of the decaying exponential function exp(-x).

Finally, the black dash-dotted line y3 shows a horizontal line with y-coordinate 0.