This comment seems to be a diversion from the question asked.  The main point of OP is that solving A x = b is commonly done with factorizations of A, not by explicit computation of inv(A).<p>Resorting to a numerical minimization (like MINRES) would be unusual unless the dimension is much bigger than hundreds.  Certainly it&#x27;s not relevant in a graphics computation with dimension of 3, 4, or 6.  My laptop inverts a 4Kx4K general matrix in 1.5s.  It solves a 4K linear system in 0.5s.