In the following video (exact second) the guy is explaining that he wants to minimize the squared error to find the best approximation for an overdetermined linear system.

[youtube]taty6lPVcmA?t=1393[/youtube]

Here is my problem. How can this:

\(\displaystyle

|| b - M a || ^ 2 =

\)

become this:

\(\displaystyle

(b - M a)^T (b - M a)

\)

Thank you!