def f1(x):
    return x**3-(2.*x)-5.

def derivative_f1(x):
    return (3*x**2)-2.

def Newton(f, df, x, tol):

    while True:
        x1 = x - (f(x)/df(x))  # it was f(x) - (f(x)/df(x))

        t = abs(x1-x)

        if t < tol:
            break
        x = x1

    return x

initial = 2

print(Newton(f1,derivative_f1,initial,0.000001))