The solution to the least squares problem Ax ≈ b is given by x = (A'A)^-1 A'b, but modern solvers never form the matrix product A'A explicitly. Even for the SVD

The solution to the least squares problem Ax ≈ b is given by x = (A'A)^-1 A'b, but modern solvers never form the matrix product A'A explicitly. Even for the SVD it isn't formed.