exercise12.py

import numpy as np

A = np.array([7, 5, -3, 3, -5, 2, 5, 3, -7]).reshape(3,3)

r = np.array([16, -8, 0]).reshape(3, 1)

A_inv = np.linalg.inv(A)

b = np.matmul(A_inv, r)