completing the square in multivariate gaussian I have a question while I studying PRML - Gaussian Distribution.
When completing the square in multivariate Gaussian,

in above equation, I'm wondering why


If $x$ and $\mu$ are length $p$ vectors and $\Sigma$ is a $p \times p$ matrix (thus $\Sigma^{-1}$ is $p \times p$), you will notice that the resulting product is a scalar in both cases (I.e. dimension $1 \times 1$.)
Now the other piece of information you need is that the transpose of a scalar is just the scalar you stated with, thus the two quantities must be equal
