In example 3.4.1 we solved for x(n), n < 0, by performing contour integration for each value of n. In general, this procedure proves to be tedious. It can be avoided by making a transforming in the contour integral from z-plane to the w = 1/z plane. Thus a circle of radius R in the z-plane is mapped into a circle if radius 1/R in the w-plane. As a consequence, a pole inside the unit circle in the z-plane is mapped into a pole outside the unit circle in the w-plane. By making the change if variable w = 1/z in the contour integral, determine the sequence x(n) for n < 0 in example 3.4.1