grid = np.linspace(-5, 5)
i = 1
for A, b in zip([A_1, A_2, A_3, A_4], [b_1, b_2, b_3, b_4]):
    plt.plot(grid, stability(grid, A, b))
    plt.plot(grid, np.ones(grid.shape), color = 'orange')
    plt.plot(grid, np.full(grid.shape, -1), color = 'orange')
    st = stability(z, A, b)
    plt.scatter(z, st)
    plt.title('Method #{}'.format(i))
    plt.xlabel('z')
    plt.ylabel('R(z)')
    plt.ylim(-5, 5)
    plt.xlim(-5, 5)
    i += 1
    plt.show()
    print(*np.around(st, 3))