Figure 1: The root x1 plotted as a function of " (solid line), compared with the
approximations by truncation of the Taylor series at O("2), x1 = 1 + "=2 (dotted line), and
O("3), x1 = 1 + "=2 + "2=8 (dashed line). Notice that even though the approximations are
a priori valid in the range " 1 only, the approximation x1 = 1 + "=2 + x2=8 is fairly good
even up to " = 2.