code: def freivalds(A, B, C):
      
      n = len(A)
      x = [randint(0, 1000000) for j in range(n)]
      return mult(A, mult(B, x)) == mult(C, x)
docs: Tests matrix product AB=C by Freivalds
  
      :param A: n by n numerical matrix
      :param B: same
      :param C: same
      :returns: False with high probability if AB != C
  
      :complexity:
          :math:`O(n^2)`