so that if w is also complex we would need a 4-dimensional
space to plot a graph such as w = z
2 + 2. Most of us cannot visualise this,
and what we usually do is to have two copies of the complex plane, and we
look at points in the z-plane and see how they are transformed into points in
the w-plane. We also look at sets of points, curves or regions in the z-plane
and their images in the w-plane