# метод наискорейшего спуска
def steppestDescent(A, b, x_0, eps):
    x_k = x_0

    while(True):
        r_k = np.matmul(A,x_k) - b
        tau_k = norm(r_k)**2 / scal(np.matmul(A,r_k),r_k)

        tmp = x_k - tau_k * r_k
        if (norm (np.matmul(A, x_k) - np.matmul(A, tmp)) < eps):
            return tmp

        x_k = tmp