xtbook might write x=A^(-1)*b as the solution to the
% system A*x=b, your textbook author never means for you to compute the
% inverse.
%
% These next statements give the same answer, so what's the big deal?

S = inv(A) ;
x = S*b
x = A\b

%%
% The big deal is that you should care about speed and you should care even
% more about accuracy.  BACKSLASH relies on matrix factorization (LU, CHOL,
% QR, or other specialized methods).  It's faster and more reliable than
% multiplying by the inverse, particularly fo