I just want to know if this question is missing an x after the (A^T A). Does the question given make sense?
Follow Math Help Forum on Facebook and Google+
$x^T (A^T A)$ is a $1\times n$ vector so saying
$x^T (A^T A) \geq 0$ doesn't make a whole lot of sense.
Yes, they probably mean $x^T(A^T A)x$