def Print(f,xs):
    titles=["N","x_k","|f(x_k)|"]
    print "\t".join(titles)
    for n in range( len(xs) ):
        comps=[
            "%02d" % (n+1),
            "%.6f" % xs[n],
            "%.6e" % abs(f(xs[n])),
        ]
        print "\t".join(comps)

        
def f1(x):
    return x*x-1.0

def f2(x):
    return x**4.0-2.0*x**2.0-1.0

#....