code: def linear_exprs(A, x, b=None, rref=False, Matrix=None):
      
      if b is None:
          b = [0]*len(x)
      if rref:
          rA, rb = linear_rref(A, b, Matrix)
          if Matrix is None:
              from sympy import Matrix
          return [lhs - rhs for lhs, rhs in zip(rA * Matrix(len(x), 1, x), rb)]
      else:
          return [sum([x0*x1 for x0, x1 in zip(row, x)]) - v
                  for row, v in zip(A, b)]
docs: Returns Ax - b
  
      Parameters
      ----------
      A : matrix_like of numbers
          Of shape (len(b), len(x)).
      x : iterable of symbols
      b : array_like of numbers (default: None)
          When ``None``, assume zeros of length ``len(x)``.
      Matrix : class
          When ``rref == True``: A matrix class which supports slicing,
          and methods ``__mul__`` and ``rref``. Defaults to ``sympy.Matrix``.
      rref : bool
          Calculate the reduced row echelon form of (A | -b).
  
      Returns
      -------
      A list of the elements in the resulting column vector.