def secante(f,x0,x1,epsilon):
    """ Método da secante para a encontrar a raiz de f(x)=0 """
    x= (x0*f(x1) - x1*f(x0))/(f(x1) - f(x0))
    while abs(x1-x0) > epsilon:
        x0,x1 = x1, x
        x= (x0*f(x1) - x1*f(x0))/(f(x1) - f(x0))
    return x

%matplotlib inline
from matplotlib.pyplot import plot

x= arange(-1,1.3,0.01)
f = lambda x: x**6-x-1

plot(x,f(x))
grid()

secante(f,1,1.3,0.001)

secante(f,-1.0,-0.5,0.001)