x is a vector - (x1,x2, ..., xn)_transpose (i.e. a column vector). so when we have x_transpose*x we have x1^2+ x2^2+...+xn^2 = norm(x)^2. right... now what's x*x_transpose, i.e. column times the row? is it an n-by-n matrix? actually now that i'm finished typing it i'm pretty sure it is, but i'll still post it to be sure..